It always gets me how the exact proper amount of an ingredient seems to coincidentally round off to an even number of units. You don't often see something that requires 2.07 cups, or 71 grams.

If measurements are rounded off for convenience, a few percentage difference won't be noticeable. People would be better off acquiring a feel for how liquid a batter should be, or how seasonings smell when they're toasted the right amount, etc.