Just a protocol yes, but there still has to be one site everyone goes to on the frontend that is the default. I.e. the Twitter of #crypto and the best solution will win.
I don't think that you understand how memo works.
All sites have the same content because all of them index the same transactions.
In analogy it's like the wallets for BitcoinCash. It doesn't matter what wallet you use, you can send/receive tx from any BCH compatible wallet.
