Simple answer:

Newgrounds is for the stuff I deem my "best" or most popular stuff. Instead of putting up every flash to the website, I'm instead going to upload only the best of my works.

There's not really a slot for my typical poke-centric animations where they're too interactive to be called an animation and they're not interactive enough to be considered a game, so instead of straddling that line I'm only going to upload whatever I think belongs here.

That goes for art too.