Part of it seems to be that I've yet to attend a wedding here in the PacNW where those kinds of dances were a prominent feature of the wedding. I've never done the chicken dance or hokey pokey at any of my cousins' weddings growing up, or any of the weddings I've attended as an adult, so I think it would be kind of weird to do those sorts of things. They seem to be the kind of thing that stays in the roller skating rink here
I double-checked with my SO to ask him if he'd ever done the chicken dance at a wedding out here, and he said no, so I think it must be a regional thing.