Keep in mind that I have 64 solar panels for my 2,300 sq ft home. And it provides 80% of all the power I need year round (less in the winter, more in the summer). Now it's an all-electric home, and that includes charging our EV to drive 1,300 miles per month (the charging done at home, not counting when we charge it away from home on trips). Providing me with 80% of all of that ain't shabby -- but it's still a long way from 100%. And that's just for one family.
There's simply not enough roof space on most businesses to come close to 20% of their power need. Why should they bother going through all of that just to save 5% or 10% on their power bill?
They shouldn't and they won't as it doesn't make economic sense in most cases, though, some of the large warehouse might generate more from their flat roofs than they need inside - factories, probably not, small business probably not. Though they just built and In-n-Out burger near my office that has a solar panel "shade" that feeds into the restaurant and also the car chargers in their parking lot. If you're going to do it, do it as best as you can and again surface area is the key to it all.
But if taxpayers are putting $10 billion into it via subsidies (like we have a choice lol), it makes more sense to install the panels as close to the demand as possible. That would help make up the 20% shortfall you are experiencing in terms of capacity vs usage if it were fed back into the grid.
Curious, do you have on-site battery storage as well?