For a lot of people, the only land they own is their roof.
Elevating solar panels also protects them from the shade of other objects.

That said, you can decouple the location of your house and the panels.
That's called "community solar," and it often takes the form of co-op ownership or power purchase agreements.
Unfortunately, it's a legal grey area in most places due to the political power of utility monopolies.
Look it up where you live and see if anything's happening in your area.