There was a reddit-style platform called Bitvoat set up a few years ago, where you could tip people in either BTC, LTC or Doge.

But not much tipping went on (though a little doge got distributed). People are too cheap to reward others with their own money. Steemit works only because your upvote distributes from newly minted coibs from the blockchain, you arn't actually giving your own coins away.