Because we already pay for roads through taxes, and car registration fees, and drivers license fees! Meanwhile the money that gets put into tolls doesn't get returned to infrastructure we agree with. It goes into company pockets who then monopolise the roads for decades and providing awful service.
It also penalises the poor; everyone in a BMW/Audi can pay the tolls and travel in comfort but the rest of you need to go to cattle class in the bus. Ummm, subsidised by everyone else of course.
You don't get to make money off of the commons just because you're unhappy that - you know - commoners are using it "too much".