If I was rich and worthy I wouldn't use a dating site. If I was beautiful and charming I wouldn't use a dating site. I can only assume there's a huge unclaimed pool of clueless rich twats and foxy bitches out there, and that the rich twats are clueless enough to want to marry one of the other set despite there being nothing but cosmetic legal or social cred attached to marriage.
I found my husband on SeekingMillionaire, and I divorced him six months later. Mission accomplished.