Well, do you know about totem/spirit animals. That may have significance to people (I know it does to me). It may carry so much symbolism that, yes, someone may want a permanent reminder of it inked on their body.
What other people get tattooed is of no concern to me. I don’t give a shit if they’ve got Tweety’s name, or a RIP…it’s something they wanted. It means something to them.
That’s a pretty subjective question. I suppose that if people want to, what’s to stop them. Would it not be better to ask if there is anything wrong with it?