It adds an extra level of permission where each extension that doesn't ask for a specific website is, by default, locked out of every website, and you have to enable it manually by either clicking on it, whitelisting the websites where it can run or globally (example pic, sorry for not being in english: http://puu.sh/q5QFR/d6004da3bb.png)
If it was, it would make Chrome all but unusable to a very large portion of its users. Once they realized Flash didn't work on any websites, they'd switch back to Internet Explorer or Firefox or Safari, rather than trying to figure out why it does that.
Flash is built-in to Chrome. You'll have to invent another straw man.
In fact, I recommend Chrome to unsophisticated users (hi Mom!) who need access to flash content. I tell Mom to never install anything ever. (She's managed to get malware on her Mac, even though I keep reminding her not to ever click on anything that says "your computer needs updates", etc.)
I don't think this would be that big of an issue really, because Flash is built into the Google build of Chrome. It's the one "extension" that would be really easy to give a free pass on this policy. This would probably be more of a nuisance on Chromium builds.
chrome://flags/#extension-active-script-permission
It adds an extra level of permission where each extension that doesn't ask for a specific website is, by default, locked out of every website, and you have to enable it manually by either clicking on it, whitelisting the websites where it can run or globally (example pic, sorry for not being in english: http://puu.sh/q5QFR/d6004da3bb.png)