Ironically most of the useful flash applications/games etc wouldn't run on these runtimes as they are using features not supported in HTML5. This sort of thing works best for crappy adverts and banners, which no one really wants anyway. This is highlighted by the fact the big competitor (Gordon?) is developed by the Google ad sense team ;)
Unless you really loved the flash IDE which I guess some people do...
I'm genuinely curious, as I do a bit of html5/webgl and formerly did a lot of flash/haxe, so I'm wondering what I missed...
However there are other things, like webcam/device support, some audio stuff, filters that may be very slow on a canvas and hard to run in WebGL inside other panes (overlays etc).
Users want to watch videos, they don't care about the technology under the hood.
Do you ever try and watch youtube videos that say, "this video isn't available on your device"...
https://news.ycombinator.com/item?id=6558539
I guess you could ask him for more details.
And you remember who Gordon Shumway is right? ( https://en.wikipedia.org/wiki/ALF_(TV_series) )