Earlier quoted context omitted.
I blame it on never understanding the UI, the way it did things, or its usefulness. It's like a chat you can't delete things from, and everyone sees what you type and all your mistakes? And you can post pictures? I just don't get it.
The incredibly powerful, federated, open protocol/platform was what excited us geeks. The client always sucked and was, at the most generous, a tech demo of things the protocol/platform was capable of.
The client should have been nothing but a tech demo. The potential power of Wave was in that it could move totally arbitrary data between independently federated servers, and had support for robots that could manipulate that data in arbitrary ways.
It could have been a Facebook/Twitter/Flicker/Whatever killer, but Google got tied down with working on the bloated UI rather than building out the platform and letting others handle the frontend of it.