Neither of my younger brothers pay for cable (we grew up without it) but I can assure you they are aware of OTA TV.
What they probably are unaware of is that compared to what we grew up with, there’s a TON of channels readily available now. I would say that when I was allowed an antenna on top of my condo building, I could get 50-60 channels compared to the 8 we had on a good day growing up (only about 20 miles away from my condo).
It could very well be that they are aware that OTA is a thing, but are unaware how much more it offers now and how much better it is than when they were kids.
The more I think about this more this must be the case, but perhaps everyone enjoys the narrative of “stupid millenials” a bit too much.
As someone in this age group: I’m pretty sure it’s what @anon75430791 said. My family had cable, but when I used OTA the only channel I ever got consistently no matter where I lived was PBS. Sometimes I could get…fox? I vaguely remember watching some snowy Digimon.
