Indeed they do a lot of moderation all of them. My opinion is that misaligned economic incentives cause all of these services to be a bundle of smaller services. The wrong economic incentives discourage protocols from forming in the smaller services to be bundled afterwards to the whole, which is called social networking site.
The smaller services could be: UI <protocol> Algorithm (Cpu, Gpu) <protocol> Disk Space. If the whole service was designed like this using well defined protocols, then we could use, the UI of facebook, the algorithm of twitter, and the disk space of instagram, or any combination.
The same could be applied to cars. It could be defined like Engine <protocol> Hood (car shell) <protocol> Peripherals (lights etc). That way we would be able to use one's car engine into another car's hood etc.
I think eventually that's the way everything is going to be designed, alongside with cars, buses etc, using protocols (ISO etc), and software as well. It is just that, it takes a while for the right economic incentives to get established.