Stop Me If You've Heard This One
It is the future, and Earth, humanity's home, is lost. Perhaps it was a disaster, an asteroid, solar flare, alien invasion; perhaps we used up all of our Resources and found none nearby, or were unkind to tropical forests, or used the wrong kind of spray can. Regardless, the remnants of humanity wander the universe, ever seeking for a new home - a new Earth.
We're wasting our energy making fun of go-go boots, gung-ho space captains and robots with vibrato voices. This is the dumbest, most dated artifact of primitive science fiction, and it needs to go.
It's Lazy Writing
The annihilation of the human race would be a tragedy. I don't dispute that. Screenwriters do a great job of showing the resilience and inner strength of humanity with this device. It's a shame that they hitch these sprightly and engaging characters to such a worn-out, creaky plot device. How do I get this ordinary person to space? they ask. Why, saving the entirety of humanity just might motivate them.
In the olden days humanity leaves Earth because they can. Heinlein imagined old-fashioned wagon trains walking through teleporters as cowboys whooped; Bradbury's new Martians set up homesteads in the ruins of ancient cities; even such OOPARTS as Michael Shaara, now much better known for his novel about Gettysburg, wrote stories with the future colonization of space serving a very similar role to the colonization of the West. Wagon Train to the stars.
Somehow that's not as popular anymore. The man with one of the greatest claims to being a real-life science fiction figure, Elon Musk, is planning a crash program to colonize Mars, for the stated purpose of providing a reserve humanity of something should happen to Earth. The goal isn't resource exploitation. It isn't an invigorating environment of danger and adventure, the opportunity to plant the Muskbanner on strange new worlds. No, it's making sure life can go on. It's something so petty as the desire to make sure some humans stay alive.
What's it really worth if all we save are a few Last Men with fancy Tesla rovers? And for all the technical skill that's going into the Muskmission, they're still going to put everyone that goes with them back down into a gravity well.
It's Lazy Science
There's the other problem. Even in the classic SF examples I mentioned above, they're just colonizing planets. They'll send pioneers for the arrows and settlers for the land, build wagon rests into villages into megalopoli, and eventually get just too crowded again, and presumably repeat the process (if they don't return to Earth en masse to fight a war offscreen, I guess). The frontier types are going to have to move. They can't have it all.
Space isn't like other colonization. For one thing it's impossible for humans to live there unassisted. We can only live in habitats, little bubbles out there. That puts obvious and urgent constraints on human expansion. Authors and screenwriters can get around this by having human-ready planets scattered around the galaxy, all ready for the one surviving starship of humanity to set down and have a new Earth. Our own solar system is not so habitable, but we get around that by talking of terraforming Mars here, building domed lunar cities there.
For another, it is, currently at least, very expensive. You need a structure, packed with rocket fuel and babysat by engineers, and the size of the Statue of Liberty, to get a package smaller than a freight container into orbit. You need a structure the size of a small skyscraper to get a package smaller than a freight container to the Moon.
What we find when we get out there, though, is that it's easy to go anywhere else once we're away from the 6x10^24 kilograms of, mostly, unreachable iron that gives us the more-or-less 1g of gravity that structures our lives. And here you have the remnants of humanity, let alone our pioneers, clamoring to put themselves in another one.
Gravity wells are cages.
I want you to ask, the next time you're subjected to some lazy sci-fi movie where a self-sustaining, perfectly functional colony ship is putting everyone in great danger by gallivanting across the galaxy looking for Humanity's New Home, didn't they just stick around Earth, build more colony ships, and live in those?
Take an asteroid. Hollow it out. Spin it for pseudogravity. You now have a new home for humanity, or at least the humans you like. Everyone else can get their own asteroid. You can build a ring. A cylinder. The intrepid fringes of science fiction have produced dozens of better places to put people in space than a starship headed for Alpha Centauri.
There are at present count something like two hundred million asteroids, and we keep finding more. Every single one of them is easier for us to access, right now, than the core of the Earth. Many of them are easier to access than Mars. Some are easier to access than the Moon. None of them have a gravity well worth worrying about. They have every resource needed for humans to survive and thrive.
And here's the bonus: every single one of them is more mobile than any plot of land on Earth.
So far I've been talking in practical terms, of preserving the human race mostly in SF stories but also in policy. Now I'm talking about how our lives can be materially and philosophically improved by space colonization.
Imagine being able to move your homestead. They're pretty isolated, true. Isn't that wonderful? Imagine a speed of light barrier between you and anyone who wants to mess with you. Imagine being able to attach rockets to your ranch and move away from your nuisance neighbors. Space offers this promise. Way more exciting to me than the idea of finding some new planet to turn into Earth again.
We All Can Do Better
Let's make movies where man has expanded through the solar system, colonizing every rock he can reach with his hands, all of it in constant, frenetic motion. Let's write books without having to come up with some contrivance to break the speed of light, instead using that speed limit to add drama, to restore the romance of the old world where some journeys just take months or years, no matter how much you want to meet your lover now. It's a fantastic plot device and it grinds my gears when almost nobody uses it.
At the bottom of this piece is my desire for a piece of land to call my own. That I'll always be able to call my own. That my posterity will also always be able to call their own.
I love the land I grew up on, and my ancestors loved the land they lived on too, but all of us had to move. It wouldn't have been nearly as traumatic if we could have taken the land with us.
I want my descendants to be able to live like Pecos Bill's mother, packing up and moving on if someone spots the smoke of a neighbor's cookfire, grumbling about needing more elbow room.
For now, that's how I'll write.