There’s always the centrally managed corporate Windows desktops. My workplace is better about this now, but previously they’d just push down updates and with some of them you’d have little other choice but to let it proceed no matter how inconvenient the timing.
Safari is holding back the web with their old, quirky, outdated engine. However, as Safari’s engine is the only option for iOS, most web developers can’t afford to ignore Safari because they can’t ignore the iPhone. So it’s IE all over again - an old, outdated browser that everyone nevertheless has to support as a significant portion of the users are using it. In some ways it’s even worse, as iPhone users don’t have any choice due to Apple’s restrictions, but even in the darkest days of IE’s stranglehold on the web Microsoft never restricted what browsers you could install on Windows.