I've been reviewing ExtJS for porting a pretty sophisticated web app from Flash/Flex to HTML5, and I definitely like what I see in ExtJS (component-centric, MVC framework, DOM-abstraction, etc), BUT there's something that's been gnawing at me and I'm hoping someone can enlighten me.

I understand that some people might be turned off by the licensing and the learning curve, but I'm really surprised that there are so many developers preferring the JQuery+UIplugins route. I know it's not a very scientific survey, but when I go to monster.com, i get over 70 hits for 'JQuery' and just one lonely hit for 'ExtJS' (whose ad only mentions ExtJS along with a bunch of other frameworks).