When he's in Buffalo, he should say hello to his fans. But he's not selling jerseys or tickets in Houston anymore.
Our culture has an etiquette of politeness among strangers. But that's among strangers who are not seeking anything from each other, but are simply maintaining the pleasant tradition of common courtesy. When status or celebrity enters the picture, both parties know that one party is probably just seeking attention with no intention of adding value to the exchange. It depends on the situation, but anyone who deals with it multiple times a day is going to be keen to it.
I've drank with and worked with a few celebrities in the past, and they'll be warm with you if you have something relevant or valuable to say. But interrupting their current activity just to get their attention is definitely of no value to them. If anything it's draining.
It reminds me of a funny story. My friend's mother is a batty and eccentric woman who loves to talk and talk without relating to the listener. She ran into Matthew McConaughey at the grocery store here in Austin, and she decided to offer him her stream of thought about what a sweet, nice young man she thought he was. McConaughey is a super nice guy who tries to be more courteous than typical celebrities, and he's just replying with "Yes ma'am, thank you, I appreciate that." And then she drops the line: "I mean, I haven't seen any of your movies, but I still think you're just the sweetest young man," which prompted his body guard, a solemn, muscular black man, to lose his **** and bust out laughing. That exchange may have provided some value to him, depending on how much he likes to get ribbed by his friends. But people of high status never know what weirdness they're going to encounter from a celebrity worshiping public.