HD video is huge - if you just rip your blurays directly they can easily be e.g. 80gb for a 13 episode series. Even reencoded you'll want to make it probably 6gb. I'm guessing you're in the US where there's a lot more available on streaming services like Netflix? Unfortunately that hasn't really made it to the rest of the world yet.
Why would someone? A lot of people are now using SSDs as their system drives. Given the cost of SSDs, a lot of people end up with 128/256GB system drives, which doesn't give them much space for non-system storage.
edit: oops, the op talked about modern games.
Additionally moving from university, internet came with residence, to moving back home, I find myself reverting back to using usb, before I used to stream all my music/video via youtube and other networks, now I download, used dropbox a lot of files, but the now I've gone back to usb. It's like travelling back in time...
I had a lot of problems with quota when I was on Rogers because my VPN connection to work could use up 30G/month when working remotely for long periods of time doing 60-70 hour weeks.
Teksavvy has never been to my house, it was just a phone call to set up the cable modem.