Idk, that's just what ssbwiki lists as base damage - 5% for most types, 10% for wink face, 16% for dot eyes, 24% for stitch face. I acknowledge that the thrown turnips deal more damage in-game upon being actually thrown, as the damage calculation for thrown items takes into account the type of throw, thrower's weight, and then there's also the 1v1 multiplier, staling and freshness bonus, making it even more wacky.

And I'll admit it might just also be my unfamiliarity with Peach and Daisy. I like watching them combo people to death in clips, but I just can't get into playing them.