Well, not quite, there are still a large percentage of video streaming websites that still require you to have the god awful Adobe Crash Player installed, while some use the somewhat more stable and considerably less buggy Silverlight from Microsoft. The only major video streaming website that has (recently) sidelined Adobe Crash in favour of HTML5 is YouTube.
Uninstall Adobe Crash Player, and if you access plenty of websites that serve up multimedia content, they suddenly don't work 100% and prompt you to install (or re-install) Adobe Crash Player. While it is still an atrociously bad piece of insecure crapware, it's still a necessary evil.
What really needs to happen is for Adobe to kill off Crash Player, thus forcing all websites that still support it, to switch to HTML5.