I think the main problem with Sneak Attack applying passively with multiple attacks is when you have multiple targets, sometimes you don't want to waste your Sneak Attack on your first attack.
Realistically speaking how often is that going to apply in practical terms?
Chances are that if you won't use your sneak attack on your first attack in the turn, you simply won't have any more chances to use it period, because "saving it for later" will mean being out of stealth.
Not to mention that at low levels more often than not your "first attack" is your ONLY attack.
Here's the thing: with an UI that is already fairly messy and convolute to keep in order, what stealth attacks and cunning actions are currently doing for the rogue is pretty much just DUPLICATING some of his standard options on multiple icons.
It's crap, frankly.
This is one of these cases where the downside is so blatant than I'd rather take any other custom "homebrew" option over being pedantic for very little benefit (and I mean in both directions: "only the first attack is going to the the one with the stealth bonus" or "ANY of your attacks in stealth/flanking/whatever is going to apply the sneak bonus").
Honestly I'm not too fond of the "toggle" idea either, but at least if it was a thing I could activate it once and forget about it.
