These are excellent criteria, I think you've sharpened the art form down to a five point guide to success. What I like about drabbles is that they give me a chance to think outside the box. Can I write a murder mystery in 100 words? Can I surprise a reader in 100 words? And because it is just 100 words, it's a good chance to try things that might not be sustained by a longer piece, or to experiment with a concept or pairing without dedicating weeks and weeks, pages and pages, to it. I think they're also a great way to learn how to end a story- a drabble really requires impact on landing, or it's wasted, and the same honing skills used in writing a drabble can be applied to longer pieces.

And now, I am done babbling!