[bld]

If you go through all the trouble to adapt to living in space for travel between the planets, why bother landing? Colonize the asteroids and short period comets, which are full of resources and much easier to access. No landing vehicles and ascent rockets are required. The gravity is so low that a spacecraft optimized for interplanetary travel can dock with them, or loiter nearby and transfer people & goods with space tugs.

Of course, it's a matter of preference. Many would still prefer to live on a planet. A dispersed civilization that includes the small bodies would be even more resilient to any one collision. More eyes out among the asteroids would also increase the chances of spotting potential collisions.