Earlier quoted context omitted.
Those were computer-to-computer, not people-to-people. The only people who could use those were technical. Facebook, Twitter, et al, built a communication infrastructure between people. That's about much more than just programming or designing computer communication protocols. It's a common fallacy from programmers to think that the hard part of "build a system for 100 million users" is the programming.
Strange, my nonprogramming mother can send emails without problems. (And finds Facebook horribly confusing.)
They were people-to-people communication infrastructure, sure, in the same way as a dirt road is a road. But there's a big difference between an 8-lane highway and a dirt road, and there's as big a difference between email and twitter. Both are a kind of infrastructure.