It's interesting, I'm 32 so on the upper end of millennial. We're supposed to be the multitasking, multiple screen generation.
But I'll visit older relatives, say 55+, and they'll have the TV on constantly and just talk over it. I find it so distracting and honestly stressful, like when you're on a conference call, your boss is Slacking you and your friend's texting about their fight with their SO last night.
My friends my age all say the same. For most "young adults," you're either silently watching TV, or you're doing something else.
My best guess is that TV has gotten louder and faster paced, but older viewers have hung on to their habits. I bet I could easily have a conversation during Cheers or '90s Law and Order, but not today's shows.