I have a 1TB cap, and while I'm not defending data caps, I only ever got to 75% usage once in 3 years of having it. That was when I got a 2TB external drive for my PS4 and reinstalled and downloaded about a dozen games at once. There are never enough games out in a single month to even get to half of my cap. I don't understand how people keep maxing out 1TB a month .
Streaming and games my friend. I stream all the time at 4k resolution. Streaming in 1080p on Netflix takes up 4.7GB/hour. So a regular one-hour episode of something debiting less than 5GB from your allotment is no big deal. However, with 4K, you've got quadruple the pixel count, so you're burning through 18.8GB/hour. So lets say you binge watch 1 season of stranger things. That's 169 GB. You add that along with games of 40-60 GB. Add that all up, add a family watching multiple streams at once and hitting 1 TB is super super easy.