In my social groups at the time(late highschool, early college) it was exclusively used for watching TV shows. The 10min limit was only a minor annoyance, and more than made up for the fact that it was free fast video hosting at time when that was extremely rare.
It was not just a nerd thing either, I remember someone I was dating in the mid 2000s bemoaning that YouTube had cracked down on TV content.
As a former megavideo user… i watched many American tv shows I wouldn’t have watched otherwise. And i wouldn’t have paid anyway because at the time as a teenager i had no money of my own to spend.
Nowadays even when paying for content, it really feels like extortion, it’s unfair anyway (prices constantly increasing, and you still get ads even if you’re paying… might as well go back to pirating stuff)
It was not just a nerd thing either, I remember someone I was dating in the mid 2000s bemoaning that YouTube had cracked down on TV content.