What's the deal with guys smelling panties?

It's scientifically proven that men are drawn to the smell of couchie but when do men stop sniffing panties? My boyfriend told me he smells my undies just for fun when I'm in the shower ... is that weird? It kinda makes me laugh bc he definitely can put his face in the real thing .. but I thought guys grew out of that .. idk ... please advise .. I need opinions on this