I think regular users miss out as well. Some of the changes that Twitter introduced were good for normal users (especially about embedded clients) - but I still have tens of thousands of people using my service. Presumably because it offers something which the "official" one doesn't.

I would expect Twitter to try and work with me. Twitter Cards, for example, aren't available through the API.

Why does Twitter need a unified experience? Email doesn't have one. Nor does any other form of communication.

Twitter could have asked us to show their ads, or charged us for API use, or asked for community funding, or any of a hundred different way to keep developers and users happy.

It comes down to respect. They've nothing but contempt for the people who helped them get where they are. And that's sad.