The reason to answer the "so?" question is to understand it for yourself, your answer doesn't matter to me in the slightest.
> find your insinuation that my caring about my appearance and style is "immature" a little offensive. //
I don't think it's immature to care about one's appearance; I do think it takes a particular development of character - that usually comes from maturity - to feel a desire to conform one's appearance to a particular pattern but look beyond that, and learn to accept it.
Along with that I'd note that appearance is often all-consuming for teenagers, and less important for most people as they age (things like functionality and longevity, say, become higher priorities than the simple look of a thing).
All that said, I'm not sure why you're so hostile to my opinion: as you say your life is not mine. If you're content in that then that's showing just the same sort of developed, mature, thinking.
[TL;DR] So, I merely suggest you answer for yourself why "I enjoy looking good" and _consciously_ decide on the weighting that has in sartorial and other aesthetic decisions.
Which, I have. It's the fact that your original comment has unneeded swipes at complete strangers maturity for expression their opinions and worries regarding what they find attractive in themselves that I have issues with. If you can't see why one could read your messages in that matter, then I'm not sure how else to explain it I'm afraid.
[TL;DR] Being bald looks gross on me. I don't like that, because I like looking nice. This isn't a sign of immaturity, as much as you keep repeating it as it that'll make it true.
If you think I've claimed someone is immature then your reading comprehension or logical model is lacking (now you have something I actually said that you can feel offended about).
If my cup of tea isn't hot then you presumably assume it has ice in it.
Because I enjoy looking good, where looking good is defined by my own aesthetics. You are not the arbiter on what I get to spend my limited amount of "focus" credits on in life, and I find your insinuation that my caring about my appearance and style is "immature" a little offensive.
Your life is not my life. Pretty straightforward.