Gone are the days where prospective moviegoers would roll up to the theaters and gawk at the board for their next watch. Theaters are trying to make up that business in other ways.
Put the subtitles on the screen! Why would anyone go watch a movie they can't hear? Tell people what the actors are saying. Theatres won't bother to compete with the home video experience of watching a movie with subtitles.
Overall, half of respondents said they use subtitles regularly.
Personally I've always done it since my youth as well (around '96.) Admittedly that was mostly because I mostly used my TV to watch late at night instead of sleep... But it wasn't even unheard of then to prefer subtitles. And it was pretty common at the HD switch over, often citing bad speakers (both quality and physical design.)
Coming from a not English speaking country where subtitles instead of dubbing is the rule, it's kinda the opposite for me. Subtitles allow me to see at a glance what to expect, so I'll have an easier time focusing on the dialogue. I have some kind of hearing impairment, so that while my hearing is very good, it only takes a little bit of noise to muddy speech so that I really struggle to make out words.
That said, subtitle translation quality has been going downhill fast for the past 15+, and that has made them a lot less useful. Especially with companies like Disney and Netflix not caring one bit about translation quality, only how much they cost to make. When you're watching Star Wars and they start talking about attack helicopters, it's time to switch off the subtitles.
Anyway, I'm sure it's largely down to habit. If you've grown up reading subtitles and it's perfectly normal to you, they're not distracting and you don't spend a lot of time on them. I can easily see how it could be a completely different experience when it's an exception and not the rule.