When the popularity of your business has been built on the back of third party services and additions (hashtags? Retweets?) there's a certain level of expectation you're not going to turn around and stab them in the back.
The word "tweet" to refer to a post. A bird as the logo! Twitter started as barely more than a faceless service, and most of what is "Twitter" as a brand came from its users and developers.
Not that there isn't precedent for their model. I remember being fascinated to read that the Big Mac and Ronald McDonald both came from local franchise restaurants, not corporate HQ. It's just a frustrating position to take. It feels short sighted.
A really cool fried who suddenly shows up for lunch in a suit, then eventually stops calling you. Your mom reads about them in a magazine and excitedly tells you what they're up to for a few years, then you stop hearing about them.
why anyone would expect a business to do anything else is beyond my understanding!