Being someone who is generally good for commitment, it amused me to notice that I don't like the idea of getting a tattoo. It's not about how people would judge me or anything like that. I've realized that the commitment with a tattoo is different than committing to a team or a partner. What I don't like is relinquishing my choice.
With a tattoo, you're committed to having it, forever (forgetting the imperfect removal techniques). Forever is a long time, and it doesn't leave much room for change. Even if I chose the perfect thing to get tattooed on me, theres still a chance that I would change and then no longer want it there. However, I can't get rid of it, at all, thus it is a restriction.
With something like marriage, there is still an implied lifelong dedication (although this is becoming less the case). It is different, though, for the exact reason that there is dedication. Making a marriage work over the years is fulfilling, because it's difficult. The tattoo, conversely, just stays on your body regardless. Also, like I mentioned before, you couldn't get rid of the tattoo even if you wanted to, which leads to a feeling of restriction and lack-of-control. By maintaining the other kind of commitment, the person gets to feel in-control because they have the determination to do it.
Tattoos, therefore, and other life-long commitments are very different. Don't confuse 'em!