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.
Well, in S*****a I've regularly found my rogue in a situation when she had to risk AoO from an enemy with several HP remaining because I didn't want to waste 5d6 sneak on it, instead trying to move to a thicker one and put the sneak to a better use. Because there is no such toggle / choice there, and first hit in a round delivers sneak damage, whether I like it or no.
Sure, it's more difficult to see in BG3 with its unconstrained hide, and it's level 4 cap thus sneak being 2d6 at most, but still. Toggle would add to the dreaded hotbar clutter, but it seems the least of all evils, as of now. Maybe if Larian will add some modifier key (Ctrl or Shift maybe) to toggle sneak dynamically, that would be better; barring that, well, yeah toggle it is.
