Except data caps still won't prevent the actual problem, I already explained above why. Even if you pretend it's a psychological deterrent - it's not really a solution to the technical issue. And ISPs will try to avoid admitting the obvious, that caps are a convenient tool to rip everyone off.

If they are worried about congestion, they have only two things they can do: 1. build their network up. 2. start reducing bandwidth of each connection, if they are too many of them.