I don't know enough about Flash, is there a downside to this? I never hear about newer versions of Flash causing compatibility issues.
… is there any reason someone wouldn't update their Flash player? …
… Has an update to flash player ever caused compatibility problems with flash based videos and applications? If not, I see no reason not to update it or for Apple to force the user to keep it updated.
Adobe has a very poor reputation for its approaches to uninstallation and installation. Managers of managed environments, especially Windows, may be acutely aware of that reputation.
The Develop menu of Safari
… don't have it installed … safari in developer mode and use the developer menu to kick it over to chrome …
+1
and I sometimes prefer to open the page with Chromium.
Either way, I find it increasingly (pleasingly) rare for a site to require a Flash Player.
Thanks – YouTube says HTML5 video ready for primetime, makes it default | Ars Technica (2015-01-27).
Since requirements for Flash had become rare, it's no surprise that I wasn't even aware of the transition.
(A few weeks ago, just one YouTube page appeared to have trouble with HTML5. I ignored it.)