Competition with bootstrap is healthy. I consider bootstrap to be the Prototype of the css framework world, and I'm waiting for a jQuery to come around.
Just saw in the job posting for Amicus:
"Open source projects, including our own in house, soon to be open sourced, real time Model View Presenter javascript framework with bi-directional data binding"
Are the existing libs so bad everyone has to reinvent the wheel constantly?
In a sense we need our MFC for the web.
To actually answer your question: yes. Existing libs for building large scale apps are in a transition period from server-side only apps to something more akin to native apps, and no one has come up with a great way to do it yet.
Honestly I hope people keep "reinventing the wheel". Web Development isn't in a place where we can just accept the state of the art and call it a day.
Web developers are an utter fucking embarrassment and shit like this is exactly why.
In particular:
Be civil. Don't say things you wouldn't say in a face to face conversation.
When disagreeing, please reply to the argument instead of calling names. E.g. "That is an idiotic thing to say; 1 + 1 is 2, not 3" can be shortened to "1 + 1 is 2, not 3."