I know I’m jumping in late. I tried to post this last Fri, but the hamsters regurgitated it. What follows is my personal opinion - certainly not to be confused with any objective or reasonable perspective.
For a long time, I operated under the assumption that there were some loosely accepted near universal standards of attractiveness. Not in a fashion model or athlete extreme, but along the lines of healthy, clean, and reasonably groomed. To the extent most people I knew paid attention to their appearance, they seemed to aim toward these sorts of common appearance ideals. Some people were more successful than others, and some put more effort into it than others.
There were always those who said, “To heck with convention,” and refused to follow the common practice. But their actions were generally of omission, rather than action. For example, guys who would let their hair grow or grow beards. Or women who would not shave or wear makeup.
In the last couple of decades, it has been increasingly more common for people - generally younger people - to, in you word, modify their appearance through intentional efforts. Whether by piercings, tattoos, or colorful hair. This strikes me as qualitatively different than the passive nonconformism of the past.
As I am always interested in wondering why my fellow species-members act as they do, I wonder about their motivations. I really could not care less what an individual (other than my immediate family) does with their body. But I admit that I do not understand why someone would affect their appearance in this manner.
For one thing, I personally do not consider it attractive, nor does it comport with any idea of “attractiveness” I am familiar with. It surprises me that modifiers often take active steps - often expensive and painful - to pursue their goals. It strikes me as curious that members of the same species as I can differ so much on what we consider desirable appearance. Finally, tats and many piercings are permanent. I know I do not view things the same as I did when I was 20 - half my current age. Looking back at things I did when I was younger, I wonder whether modified folk will one day regret their choices. A moderate tat here or there can be downplayed. A pierced ear can be allowed to close up. But a large tribal or ear plugs are forever.
Enjoy it. I don’t understand it. But there is no reason you should conduct your life, or treat your body, in a manner I choose or understand.