Values like that always seem really useful, but I can't help but think I would never be able to apply them in game. I've been judging on pure instinct whether or not I can crouch cancel stuff for years, so I feel like I'm good enough at it that trying to remember percents would only clutter my thinking.
Of course, I can't resist myself, so I've actually been compiling a bunch of stuff for kill percents of different moves. I've only actually done the percentages for double shining people off the top of YS (at all 3 heights), but hopefully I will also get around to when uair kills sooner than a second shine, usmash, and dtilt. Of course they are based off of training mode CPUs who aren't DIing, so people may live longer, but I think it would at least be useful to be able to go into a match thinking things like "okay, as soon as I see Jiggs at x%, I can usmash her and she will die if she doesn't DI it."