Because it's a sign they've been brainwashed by mass media and mainstream pop culture.

>heh, imagine not liking tats, you are a stuffy square
They're not getting them to "rebel", they are getting them to conform. Mainstream media presented the subculture to them, they think it will make people think they are cool and edgy, so they went though the trouble and expense of having ink injected into their skin and piercings. If they were being original and didn't give a fuck what people think, why would they get tats like everyone else specifically? If you were going to come up with an original idea 99.999% of the time it wouldn't be tats, it would be a bright pink spandex onesie or a pogo stick or something.

>but these are based and trad tats!
Is she a Caledonian Pict from the 2nd century AD? Maybe if there was an apocalypse and they became symbolic of something during the struggle it would be genuine, otherwise it is just more slop. It is not a big deal, it doesn't mean she is le bad or can't change, just being wise to the social trends and psychology behind it.