It's for graphics/video/audio professionals, the original Mac "pro" market, where it's a super-useful ultra-flexible slider/picker that works far better than a trackpad or mouse for that purpose. And the ones I know love it.
I get most HN'ers don't like it (and I personally have no use for it), but Apple didn't build it because they're dumb or are going for style over substance. It's just a different target market.