I want to put games and applications directly on the blockchain. This means that the smallest tick of time on Steem is three seconds. 3000 millisecond lag will not be acceptable for some applications. Also, right now each account can only comment (put text info on the blockchain) once every 20 seconds... another (self-imposed) limitation.
EOS is already ahead of the game with 0.5 second blocks and multi-threaded applications. This obvious upgrade makes sense considering @dan was the mastermind behind both projects.
I suppose a side-chain is kind of like a thread. To be honest I'm not quite sure how EOS implements multi-threading... only that it does. If we consider smart contract platforms to be the operating systems of the Internet, multi-threading will be a requirement of the future. Imagine having a computer that could only run one app at a time. It would be near worthless.
Interesting, I didn't think of that aspect of the technical challenges of gaming here on the Steemit blockchain. It does present challenges for sure.