I keep saying this, I am very happy with my ISPs data cap. It is 250GB, I never hit it. If I do I can buy a few extra GB for that month, or have a very slow internet speed. If I need more than 250GB every month, there are plenty of nice upgrades that cost extra. Not only the cap goes up, but the internet speeds get ridiculously fast. Nice!
My parents, my parents in law, brother in law and my many sisters all have the lowest subscription with 250GB a month. None of them hit the limit. Ever. (Yes, my many sisters have many children that watch youtube) The in-laws do not reproduce in large numbers.
My tech fancy colleagues on the other hand complain about datacaps a lot. 250GB is way too low! What is this, the middle ages? The culprit? Watching tv shows in 4k and HDR on their fancy over the top OLED displays. Oh yes, they do download a linux distribution. (over and over I guess)
Let them pay extra for that. They love complaining about it.
* I live in Belgium, ISPs actually do invest in their networks here, it does change the story a bit, I think.