It's like a lot of things in life. It depends and it can be complicated.

Upfront costs for infrastructure besides the panels themselves is expensive and in places where electricity is already cheap companies won't bother.

You also have to conduct tests to ensure that the grid and transformers can handle more power, and if they can't then you have more infrastructure that needs upgrades.

I'm not saying we shouldn't do this. We really need to in the long run but it isn't something we can simply snap our fingers and do instantly.

Also, a lot of the unprofitability comes from VC culture in my opinion. The individuals at the top of businesses often times won't stick around with the business long enough to start see the savings from solar energy.