It is modern morality with out better understanding of psychology and brain development that lead many people to believe that sex in extreme age differences and extreme power imbalances is fraught. And in many cases, immoral. Regardless of whether the young person is a day under or a day over the "age of consent".
I would posit that cases where a 17 year old is sleeping with a 55 year old and it is NOT due to some form of coercion, are extremely rare.
Only if you assume that for some reason minors are pure and always operate rationally and "morally", thus it is just impossible that a 17 year old has decided that, yes, they want to have sex with a much older person. And somehow when they turn 18 their brain completely reconfigures.
Because I've been 17, I've had friends that age that wanted to do just that by their own accord, and some that have gone through that fantasy, without being coerced whatsoever. It's a bit weird, not really my cup of tea, but I know what being a horny teenager feels like.
While I am strongly in favour of 18 being the arbitrary threshold of consent, we as society need to remember that teenagers become sexual beings much earlier than 18 years old. It's simple biology, and I wonder if many of these "prudes" have lived a weirdly sheltered childhood and have not experienced normal sexual development.
So "posit" what you like, the rest of us live in the real world where 17yo girls at a nightclub are crazy, rebellious, and very horny.
You do need to be able to dance well, you need to pay the bill for the whole table, and you need to be fun. That's what going out is for, that's why people are there.
Me, I'm old and married now but not a karaoke trip to Cyprus goes without some 17yo trying and repeatedly failing to go back to my hotel despite the ring. That's because this old dude can sing sensitive french ballads, rap-up some jay-z, or dance well while singing k-pop reading native hangul. If that doesn't work, I'll do a russian song w/o an accent, and we all know those girls are easy. I'm fun, I'm not fat, and that's all it takes.
That 17yo btw. That's probably your daughter, and the more you lock her in to a repressed life, the more she'll shack up with guys like me. Choo-choo!