Where are the HTML5 web adverts? They don't exsist because:
1)you have to code things 4 times (once for all the browsers + fallback)
2) There are no artist friendly tools (google's flash translator only works for chrome, see above)
3) Everything looks different in each browser
4) JS animation is Sllllloooooowww
5) Animation primitives are missing, those that exsist are from the 1960s
6) there are no mature standard/implementations (in widescale use)
with flash's workflow you:
1) create a flash file with the mature tools, test, release
2) create an animated gif as fallback
yes its buggy, and the video is slower than decent native support, but it works the same across all browsers (90%)
Considering that animated advertisements are the scourge of the Internet, if it weren't for the legitimate uses of the things you mention, I'd consider the crippledness a feature.
Advertisements should be text or images. Even animated GIFs are pushing it.
with flash's workflow you: 1) create a flash file with the mature tools, test, release 2) create an animated gif as fallback
yes its buggy, and the video is slower than decent native support, but it works the same across all browsers (90%)