There are significant risks on some of those deals, as, if the toll highway doesn't get enough traffic, governments will lack the political will to let the road decay, and often will end up buying back the highway, and paying for the repairs.

So if the highway goes well, the company makes money hand over fist, and it all looks like a giant scam. If it goes really badly, the government takes a bath, and it all looks like a bunch of waste. So ultimately it's very difficult to set up a deal that lasts very long and doesn't seem like a regulatory mistake, one way or the other.

Also note that this isn't purely a US situation: Some form of privatization of toll roads happens all over the world, and success rates are also not all that great