You have a permanent scar on your skin that is very difficult and expensive to remove when you realize your mistake. If you have an exposed tat, it might make it difficult to get some kind of jobs and people might think poorly of you for having made such a decision.
I've often recommended people get a temporary tattoo that will impress all your friends but wear off over time. Obviously, not a big fan of tattoos. If someone has the opposite opinion, fine. I just gave you mine.