Almost too many side tokens. Technically, these aren't different platforms. They all run on the same blockchain. The content is simply organized into each frontend when the tag is used. The SMT and communities Steemit Inc is rolling out soon will be similar. People wanted SMTs and communities for so long, were sick of waiting, so a group of dedicated Steem enthusiasts just built their own. That's all the tribes are. Those aren't knockoff platforms like whaleshares or whatever. It's still Steem.