It makes far more sense to have a separation of concerns. By having roofing and solar separate you can address problems with them independently. If you combine

It makes far more sense to have a separation of concerns. By having roofing and solar separate you can address problems with them independently. If you combine them suddenly a problem with one is a problem with the other. This principle applies to most things in life. Having a dumb TV and a separate internet connected streaming box, a computer with a dumb monitor, an audio amplifier and standalone speakers, etc. Combining things typically makes their initial setup easier but in the long run they cost more and generate more waste.