This illustrates why people are jumping for Processing.js, even if it cripples many of the things that make Processing cool. Paul Downey inadvertently hits the nail on the head:
… somehow hadn’t got around to actually doing anything with it. You see it’s the whole Java thing that puts me off; when it comes to playtime life’s far too short to wrangle a CLASSPATH or compile an applet.
Ah-hah — there’s the reason: developer laziness, and fear of Java. And rightfully so. Configuring a full-blown IDE for Java can in fact be some effort — I think it’s well worth it when you’re doing lots of work over time, but what if you just want to sketch?
Here’s the good news: Processing’s "founding fathers" Ben Fry and Casy Reas agree with you.
In case you’re interested, what Paul did is reasonably cool — he set up Processing.js inside TiddlyWiki, the personal notebook tool.