The fact is, Flash isn't supported on mobile devices. It's merely possible on Android. Sure, you can't blame the restaurants (you don't need to blame anyone), but "simply install Flash" isn't true.
It sounds as if you love saying it.
Anyway, I agree with gp: so many restaurant websites seem to focus on being cool more than on providing the information I need: address and menu. And yes, Flash is a big part of this but even if that worked on iOS, these websites would still be annoying.
And "simply install flash"? It doesn't work on iOS, it hasn't been supported on Android in over a year, and has stability issues on Jelly Bean. I could almost be convinced that you're being facetious...almost.
I doubt that restaurant owners are thinking "So my customers can't see my website? I don't care, it's because they picked an Apple device and everyone knows Apple devices are shitty!"
Um, what?
And do you really hate saying it?