unfathomable sheep-like behaviour in humans

I realise I am middle aged and I that grew up in a world in which only a minority of men had tattoos, and they were either sailors, builders or thugs. Then, around about 15 years ago, David Beckham, famous footballer, gets a tattoo—followed by a string of other footballers, so-called celebrities and media non-entities, all proclaiming they are expressing their 'individuality' or 'rebelling'. Soon afterwards every young man and woman has covered his or her body in them, all believing they too are expressing their individuality or rebelling. And yet, like lemmings advancing towards a cliff-edge, or sheep flocking with the herd across fields, they all look almost the same, that is apart from  having different amounts of these vulgar eyesores, or slightly different colourings to them, they all still look virtually the same (at least to me).

I see no individuality in these people. Or any spirit of rebellion. I can't understand this herd-mentality. What is it that makes people all try so desperately hard to copy one another in a bizarre attempt to appear different from one another. It doesn't make sense.  You would think to be different or rebel, you'd do the opposite to what everyone else is doing. And what is this craving to emulate celebrities or media personalities? Do they imagine they are better than they are—smarter, nicer, more charismatic? 

The unfathomable sheep-like behaviour aside, I can't understand what, apart from mental illness, what would drive a person to inflict such damage on their largest and most vital organ.  The very idea of deliberate mutilation horrifies me.