From the first day the service was announced, a lot of us "long timers" in computers and I.T. were left scratching our heads, wondering what the point was in the entire thing? I mean, Twitter was essentially nothing more than yet *another* IM client of sorts, except with arbitrarily short limits on the length of messages.
Twitter is more than just another IM client. They invented, or at least brought to mainstream popularity, the concepts of the follow and the timeline, which were imitated by Facebook, Instagram, and a number of blogging platforms. Companies and users love the follow, because it realises the ancient mindshare goal of finely-controlled (voluntary) content push, without the clunkiness of channels and email notifications. Once you have permission to push, revenue options open up.
Twitter is not exploiting this power well. They could be earning a cut of the sales made, valuable insights gained, and joy discovered when the information channeled through their platform helps someone choose a product, make a decision, or find something entertaining. I'm not talking about ads and affiliate links.