Rooftop solar makes sense because cost of land is a sunk cost, and thus doesn't have to factor into the total cost of the install. This assumes that solar makes sense for the area though, some houses are shaded too much.
But then you get increased losses when transporting the energy into the city, plus the costs for the distribution infrastructure. Rooftop solar tied to the grid can be used by your neighbours when you aren't using it, which means almost no transport loss, not even crossing a transformer.
Sure. I was responding to a comment saying the reason rooftop solar makes sense is the sunk cost in the land overwhich the roof lives. Rooftop Solar make a lot of sense, but probably the main reason is the electricity generated does not come with the cost of having to maintain a hugely expensive grid.