Of course you can't see the ninja. What kind of ninja would allow himself to be seen when he's sneaking up on a samurai?
I think the samurai represents Flash: He's from the same country as the ninja -- he might even be a close relative -- but his moves and his costume are a lot more ostentatious, and he's got better PR. He's also owned by a shogun who controls his every move.
The point of frameworks is to write something well once. You might then iterate on the core application features, but since you use that code again and again it's cheap.
Many frameworks are larger than you might expect them to be because they take care of edge cases you haven't thought of. YUI for example is guaranteed to work in 6+ browsers on 3 platforms, as well as being tested with screen readers and other assistive technology of disabled users.
With regard to mobile devices, presumably the mobile devices are going to get fast enough to deal with it (my N95 deals with the YUI code on the yahoo.com homepage just fine) or we will make widgets specifically for those devices which are stripped down.
I think eventually we'll settle on compilers/translators which generate cross-browser JS object code from your notation of choice; like ParanScript (Lisp), Red (Ruby), and GWT (Java) with the feature completeness of today's best JS frameworks.
