I'm sure some of them are leases, but mostly what I see is that you either buy them, often over a long time with a loan, and keep all the 'profits' or you agree

I'm sure some of them are leases, but mostly what I see is that you either buy them, often over a long time with a loan, and keep all the 'profits' or you agree to let the company place them on your roof but they keep most of the 'profits'. The profits generally coming from selling the electricity back to the grid. Leasing them may make financial sense in some situations, like places where you can't sell back to the grid but still use a lot of electricity and the lease price is still less than buying from the grid directly.