They see less play because they're less flashy than other paths, and it's an old path, compared to newer shinier things... and because Totem Barbarian has long been considered too OP to really give other paths a major look in unless they're super interesting, which, mechanically, Berserker is not. Off the top of my head I can think of three people who have a Berserker barbarian in their line-up of played characters, though I'm actually not one of them myself, and that's just people I know of, so they still do see use...
