These platforms already have a their identities and I doubt they will risk integrating a system that will drastically change user experiences. Rather, projects such as Steem, LBRY(The LBRY project is a "decentralized digital library" that seems very promising), and Breakout(A gaming multicurrency platform) will grow because thay are developed on a blockchaon and can do what these platforms do to distriute content but with rewards and incentivization systems at their core, rather than slapping a blockchain on a model that is thriving today, but will likely get outpaced in the future by better alternatives.
These platforms already have a their identities and I doubt they will risk integrating a system that will drastically change user experiences. Rather, projects such as Steem, LBRY(The LBRY project is a "decentralized digital library" that seems very promising), and Breakout(A gaming multicurrency platform) will grow because thay are developed on a blockchaon and can do what these platforms do to distriute content but with rewards and incentivization systems at their core, rather than slapping a blockchain on a model that is thriving today, but will likely get outpaced in the future by better alternatives.
YouTube seems like the closest to paying for likes but Facebook could probably easily do it if they got involved with crypto