First, IMO almost invariably when they're calling you "grandpa" it's a cover for a degree of envy.Ever since I started dressing better, my friends now call me "grandpa." And I'm only mid-40's. But, to most people below 40, if you're dressing up beyond having to for work, then they look at you strangely. And I'm talking about something as simple as chinos and an OCBD. For most of them, dressing up means putting on your nice jeans and tshirt. They ask my why I'm so dressed up all the time. I tell them I'm actually quite comfortable. And keep in mind, I'm not really that dressed up. Only in comparison to them. As much as all of us like finer clothes, the majority of the young people getting older are quite fine with very casual clothes no matter what setting they're in.
Second, over the years (and I've made this observation before, here), I've observed that urban young black men will acknowledge individual style even if it's not their style (and is, indeed, far from it). When you get nods of approval for your DB suit from blinged up young men wearing ultra-baggy jeans and outsized leather jackets, you know that the barbarians are not quite as close to the gates as you thought.