The answer is simple - Chinese people is not their target audience, so they are don't need promotion on these networks. People from China can't participate in most of ICO's, so advertising of ICO on these networks doesn't make sense. And also, it would be difficult to organize bounty in these networks if manager don't understand Chinese language (as far as I know these websites don't have English version)
And it's good point mentioned by people above - advertisers mainly focus on global social networks like Facebook or Twitter where they can reach biggest auduence. They aren't interested in local social networks. Even VK.com which is most popular in Russia and 4th most popular in the world - you can't find many bounties on this network.
Those sites/services you've listed are fairly known already, and are not even related to bitcoin or cryptocurrencies in general. I don't think them having bounties will help them much.
I think you missunderstood OP. He is asking why there are no bounties on these social networks like we have of Facebook or Twitter.