Re: as soon as the browser's developer console gets opened
Same reason that onmouseblahblah, onrightblahblah handlers are allowed to disable features of the browser, and thus people have to install stuff like RightToClick? Seriously though, I saw early on in Android browsers (especially Chrome!) that you had some site load up a prompt that you thing couldn't get out of. The scummy people would often make the prompt ask you to call some tech support scam number to 'get back your phone'.
In the old days, you had replacement of status bar messages, blink tag, popups and blockers, window resizing/moving, removing address bar, loading ActiveX plugins by default, drive-by-installing, and so on. All invented by the same kind of thinking that you're talking about. "Should I?" doesn't even occur to people with that thinking.