I'm not sure that's even true. I'd expect power consumption as well as 'wear and tear' to be less, and possibly significantly so, at idle versus continuous use.
> Data caps are a measure invented to extract money, not serve customers or packets.
Some people will definitely test the limits of anything that's supposedly unlimited. I imagine you're partially correct but I suspect data caps are the most comprehensible product attribute for ISPs to limit the relevant costs.
> If the cable companies were worried about fairness, they'd really be speaking in terms of bandwidth reservations at peak times and encouraging use during off-peak hours, and similar things.
I'd imagine that'd be an even harder sell than congestion pricing for motor vehicle traffic. It is mostly just a 'fact' of the world that almost everyone is going to want bandwidth at the same times. The costs of transitioning to any other arrangement are considerable. And Netflix is probably the player most able to adjust. I'm not sure if they still do, but they did at one time host a lot of their content in ISP data centers.