Their reasons, or my reasons for thanking them?

I think their reason was that watching TV is a brainless activity, and they preferred me to use my brain. They were fine with me, say, teaching myself BASIC. It wasn't an aversion to technology in general.

They also carefully monitored the content, there was plenty of stuff they'd rather we didn't see.

Why did I thank them? Because they gave me an appreciation that life is to be lived, not wasted away watching some idiot spouting nonsense that isn't relevant 5 seconds later (if it ever was).

I wasn't the only one in my class like that (though we were a minority). But you could see the difference in those who did and those who didn't - in intelligence, manners, energy levels, and generally being better human beings.