I dont have tattoos, but I would suggest that it's a way of expressing individuality in a world where the people all around me are increasingly homogeneous.

Our living spaces, work spaces, and public spaces seem less able to express our individuality, but our body space remains our own.

Ironically when they become ubiquitous their value and interest diminishes. In a recent visit to Florida the number of folk with visible tattoos was -much- higher than I'm used to at home. Here visible tattoos aren't "rare" but uncommon. In Florida I could see 10 people with tattoos just by swivling my head.