Tinder is, IME, pretty popular for finding sex partners, and much less popular for finding longlasting relationships. This is a good thing, of course - and obviously filled a huge gap in the market - it's just not what OKC et al have traditionally been for.

OKC tends to attract people who don't fit into other platforms, and are looking for longlasting relationships. There's even plugins to help with finding interesting people/avoiding red flags within certain subcommunities - trans people, poly people, and kinksters all use it to a large degree.

Tinder is pretty popular, there are other big players in this market