Definitely agree, I have an idea for an implementation that solves the issue of having it auto apply and still be able to choose when you don't want to waste it:
A simple fix would be to add it to the toggle bar with Attacks of Opportunity, having Sneak Attack damage be automatically applied to the next successful hit against an eligable target while Sneak Attack is toggled on once during that turn. You could just untoggle it if you didn't want to waste it on a 1 hp target and turn it back on after.
