I think it's probably a good thing for now. People are still trying to figure out how to do frontend programming well. Eventually one/a few good models will come out of the chaos, and some frameworks implementing them will start to stabilize. Of course, I have no idea how long that will take.
I feel like the Ruby webdev community had a similar ethos, but I dropped out of that scene before things really coalesced. Can anyone comment on how things are playing out there?
I think this is because creating a Javascript framework is easier than creating a framework in other languages - clientside or otherwise.
Note: I didn't say making a good framework was easy, just making one at all.
Sometimes people just decide to experiment, to try something and then as they grow with it they think it's big enough to share. When a whole bunch of people do that, you end up where we are with JS frameworks.
I'm in the "it's no big deal" group. Are there thousands of frameworks? Yes. Have I heard of more than 5 of them being used extensively? No. The good ones are embraced by developers and shared. The other ones are mocked into oblivion. It's the natural order of things.