That's a pet peeve of mine too. I don't know what happens, but it seems all growth stops at a certain age or stage of development and from that time on the person wears their hair the same, listens to the same kind of music, like the same style of clothes and shoes, watches reruns of the same sitcoms, likes the same kind of people and forms of entertainment and that's it!
Anything else is foreign and alien to them or just too much trouble to explore and examine or even try.

My ex is 60. Listens to nothing but doowoop, wears the same white tennis shoes and polo shirts with denim shorts, has worn his hair the same way for 40 years, drinks the same brand of beer, watches the same shows on TV and wouldn't dance if his life depended on it. Likes only pork and chicken and order.