1. it can be turned off (in most instances)
2. bugs could be pushed (as was the case with the Firefox 126.96.36.199 canvas drawImage bug - and version 188.8.131.52 has massive memory leaks in drawImage).
3. browser platforms become moving targets.
Big corporate environments that rely on poorly coded applications that only run in a specific browser version of yesteryear may of course pass on the updates. That's a big problem.
But these things considered I still think autoupdates will benefit the spreading of HTML5 (and what other standards may come) greatly.f2富二代官网入口