Because they're old and they literally don't know better.
Pretty much this. Old people usually stick really hard to their views/habits.
I quit watching regular (as in free OTA) TV when I was 14yo, back in 1999, as we got cable then and it was
so much better than regular TV. I literally pitied those I knew who didn't have access to cable, since regular TV is complete and absolute crap more than 95% of the time.
Even then, the only good cable channels we had over here were basically HBO for decent-to-good movies, some other channels, like Fox, USA, Warner etc. some specific TV series and Cartoons, and Cartoon Network/Fox Kids (Jetix) when it had good shows/Toonami over here. Cable also had (has) a lot of useless channels that we had to pay for.
Then when "Broadband" Internet came (1 Mbps was the RAGE back then in 2005, coming from 33.6 Kbps. And I used to download full 200MB anime episodes over that slow connection, over the whole week. Thank God for DivX ;-)/XviD too), I had no more reason to subject myself to TV anymore.
The only video content I watch now (mostly anime or a random movie) is via piracy/prime video, I get the news from the Internet, and my main hobby is gaming/programming, no need for TV at all.
That said, I get the appeal of having a very passive entertainment option when you're dead tired (or lazy), and that's what TV/radio are for.