Dress up differently

 Um not sure if this is a good or bad behaviour to judge people's fashion and style according to their age. Is it a good thing to categories different types of styling and fashion wear to a certain type of age?

Why does it seem as if anyone who  is older when rocking her own legging without anything covering  seems like disrespect yet we say fashion is a form of self expression? Why is  it the case that certain clothing  are categorised for certain people?