Let me guess: you're a non-web developer? A.K.A a "real" developer.

Well, in the current web world saying "why use Javascript??" is about a smart question as asking "Why use C??" or "Why use Java??" in the desktop world.

It may have 10,000 flaws in it, but that's the de-facto standard ATM.

Furthermore, unlike the desktop realm were you install your dependencies with an installer, in the web you have to wait 5 years for the crap old technologies to drain out after the new better one comes out.

None of us would use Javascript if we had a choice, but we don't. So toolkits like JQuery or this release by Google are life savers.