I often do. Partially it means that if I'm not focusing on something explicitly I can still glance over and understand what's been going on if I've tuned out the actual words (one of the reasons I don't do audiobooks is because I tune out the audio more often than not)
But also because modern TV has such weird biases in recording. In the same way 'dark' is the new 'brightly lit' in cinematography, 'whisper' is the new 'volume' in TV - and it's not because I have auditory processing issues. I have old TV series on iTunes - stuff from the 1960s and 1970s, and stuff from this decade, and the audio balances are off, and the lighting etc makes everything darker for no good reason.
Always, ever since I was a teen staying up way too late during summer vacation. I couldn't have my TV too loud otherwise it'd wake my parents so I used subtitles instead
I don't know when it happened, but eventually I just prefer to have it on when I'm watching Netflix. Some scenes are quieter than others and I feel like I might miss something. I never liked how they looked like on cable TV, and that's the only thing that stops me from using subtitles - if it is too bulky/distracting.