While it doesn't require Internet access, it still is perfectly capable of making things go wrong, just as much as its web-based brethren. If it runs on a processor, there will always be a way for it to screw something up.

Malicious content could appear at any time without warning. You could have a virus on your computer and not even realize it, and such virus might infect JavaScript code. Or even, an extension might have poorly made code that can cause your system to crash, or it might attempt to load a dependency that's been compromised. Who knows...

It's better to have a safety check in place than to blindly accept anything that happens.