Well, I suppose there are tons of reasons if you really want to analyze it, but the bottom line, to me, is that as a society we have very little respect for the old.
To be old, to age, is something no one wants to do even though it is the natural course of things.
I hate all the terms you mentioned, and try not to use them, though I know I sometimes do.
We also make too much of "style" instead of substance, so we are quick to make harsh judgements about a person's style, as if in the end it really mattered for something.
It's sad when you really think about it, but it's never going to change.