I didn't say there's no profit margin, I said there's no profit incentive.

Government employees and representatives don't get paid more for doing innovative things, but they might get fired for doing something innovative that turns into a boondoggle. If we see more road privatization and relaxation of regulations, then entrepreneurs might show up and try things like this.

I doubt it would pay for road maintenance, at least not how they currently do it, which is unfathomably expensive. You also have to expect a high-tech solar road would cost even more to maintain.