It might be an unpopular opinion, but like others have said, I also associate tattoos and piercings with attention-seeking and a desire to be seen as tough, "cool", dark and brooding/"edgy", and "bad"/"dangerous"/wild and rebellious. I feel a lot of guys use it as a shortcut to being "interesting" when they really aren't all that unique, if you think about it. And on guys, it also has the extra connotation of being hyper-masculine and uneducated/unsophisticated, and wanting to be that way. Redneck or working-class culture, trying to offend or antagonize middle-class sensibility. Very brawn over brains, which is the opposite of what I was taught to value or what works best in the modern world. I don't know if I'm that smart but I'm definitely not a very physical person, so it doesn't make much sense for me to play to the style of a physical person. I'm definitely more of just being a regular, easy-going, friendly person instead of being one of those aggressive, dominant kinds of guys.
Then again, a lot of people are influenced by their environment and the culture they were born into. If most of your family, friends, and other peers are tattooed or pierced, it raises your chances that you'll see it as normal instead of "other". I've lived in suburbia all my life, and most people don't do that here, and if they do, it's usually not in a very extreme way. There really isn't a need to be "tough" or "masculine" around here, for better or for worse, and there isn't anything to rebel against, so for a person to act that way around here, it doesn't seem natural. It's not the culture I was born and raised in. But I do think others should be able to do what they want, even if I'm not a fan.
I probably wouldn't mind as much if I'd been raised with it, if more of my friends or family had them, if I had the interests or was going for the kinds of jobs where they are common, or if I hadn't had bad experiences related to tattooed guys (competition in dating) or could get past certain associations. I do understand, on some level, that not every person who is into tattoos and piercings is like the stereotype. Who knows. In a different life where I associated them with people I liked and things I agreed with instead of people and things that I don't, maybe I would have them myself. But as it is, I haven't felt the need or think it would make sense on me.
As far as dating goes, I don't really mind them on women as long as it's not extreme. It doesn't draw the same feelings of hostility or rivalry like it does on guys. It's kind of weird. I'm not a wild person, but I don't really fit in with conservative people either, and while I'm not specifically looking for a rebellious woman, it seems to be a side effect of what I am looking for. Which I feel makes relating harder for me.
That said - one time I went over to my friend's house, and his older brother and their friends were hanging out. I was wearing a Transformers shirt, and they said I should meet one of their friends and talk about Transformers because he was also a fan. Sure enough, he was covered in tattoos of Transformers. They were pretty good depictions of the characters, and in spite of myself, there was no way I could hate on the guy. I didn't want to. So, there you go.