Why would bother?

Assume that we are a high tech space faring species. Assume that we can fabricate some modestly large life-supporting structures in space. Assume that energy is a problem we mostly solved.

Why in the name of all that is holy would we live on worlds with: Gravity below about 80% of Earth Gravity or above about 110% of Earth's gravity, places where the partial pressures of our gas mix aren't readily at hand, places where thin atmosphere will allow a lot more radiation to be problematic, or places where water is scarce, or air is tainted, etc?

If we can do what I listed at the top, why would we not just build some reasonably big space habs around every half-way workable body in each system? We can mine some planets or better asteroid/planetoid belts for basic resources (or even use some of them as a hull structure if we are going cheap), we can use solar collectors or gas skimming to get power, and we can borrow atmo (if at hand) or ship it in or use some fancy operations using energy to create some, and we can find, transport and amend soils.

We could build Trojan Point colonies that are robust, have type 6 atmo, can be spun up to a decent amount of gees, can be protected from some amount of radiation, and that can use solar power without trying to pick it up after a bunch of its energy dumps into a medium+ atmosphere.

Plus, other than the initial construction phase, it could leave some planets more pristine (for the ecologically minded). Or, we could use robotic farming, etc. with some minimal technical support on some of these somewhat hospitable planets to grow food. Or we could create some large agro habs that just do food production.

These aren't Klemperer Rossettes, Niven's Ringworlds, Dyson's Vacuums (err... Spheres) or Alderson Discs. These seem simpler and fairly modular and expandable and designs could likely be used similarly in most systems leading to easy sources of common supply for the more sophisticated parts.

You could have a lot of small habs around a system for:

a) science research

b) military research

c) medical research

d) planetary or solar research

e) military/police/SAR

f) smaller minority communities

g) specialized purposes - manufacturing, testing smaller new crops, etc.

It seems like this would make for a less expensive option than all the systems you need to support life on planets you aren't well suited to (including atmo, hydro, radiation, gas mix and pressures, gravity, etc). I suspect on many worlds much different from humans, we may be frail or have shorter lifespans (immune system may not behave in useful ways). Genetic Engineering may be an option but that has to be costly and problem prone plus it customizes you away form many other possible planets so you might be stuck there.

Or am I way off here? Would not having some significant sized orbital habs not be the way to go?

TomB