I blame catalogues. Garter belts are worn with panties because of modesty issues, but to better show off what they look like, they were worn over top.

And I think this is what led to the big trend of garter belt over panties. Oy.

I prefer stockings to pantyhose, but pantyhose rarely fit me. If they're long enough for my legs, they assume I have a much bigger ass and thicker legs than I have, and I end up with elephant ankles and baggy knees. Or the legs aren't long enough, and I end up with MC Hammer nylons. Ack.