No it isn't! Your judging people, it's none of your business and in the grand scheme of things it doesn't matter
My hair is long and it's staying that way and I'm older. I wasnt allowed long hair has a young person.
I've had it at varying lengths over my life (I'm now in my 50 and have adult children)
I'm now in my 50s I decided just to let it grow some years ago. I have it trimmed and coloured regularly. I look after it.
I have no intention of having it shorter again. Its about three quarters of the way down my back.
Long hair means you have choices in styles you don't get if you have short hair. Updo's, down, straight, curls, waves and so on.
For me short hair bores me ridged on me. Im stuck with one style. Fine if that's what you want. Its not what others want
Though the majority of people will have different reasons to me for long hair it can just be that they like it long because they can do more with it.