Microbiology is crueler than we thought, and it makes all biospheres lethally incompatible with all others.

Food production for natives of one planet, thanks to the unknowably vast web of interconnected niches crucial to every known complex life form, can only happen on that planet.

Interplanetary tourism is generally lethal. Communication from orbit is pretty safe, and telepresence is easy, but actually breathing the air of other worlds is suicide.

So, if you have to travel, you have to take the whole thing.

c.f. War of the Worlds, and a more recent book, but, spoiler.

Now let's talk about traffic control: wow, risky! And the gravity waves?

Microbiology is crueler than we thought, and it makes all biospheres lethally incompatible with all others.

Interplanetary tourism is generally lethal. Communication from orbit is pretty safe, and telepresence is easy, but actually breathing the air of other worlds is suicide.

Food production for natives of one planet can only happen on that planet. Reproduction in general can only happen on that planet.

So, if you have to travel, you have to take the whole thing.

c.f. War of the Worlds, and a more recent book, but, spoiler.

Now let's talk about traffic control: wow, risky! And the gravity waves?