Discussed briefly in my original post. Certainly not peer pressure.
I don't see any discussion of the reasons in your original post.
But I did see this in your subsequent post:
Anecdotally though, thinking about folks I have worked with (I'm in healthcare), and those in my social circle who are fairly similar to me (highly educated, gainfully employed, financially successful, intelligent) most of us have tattoos and/or piercings.
It was the "most of us have tattoos and/or piercings" that made me ask.