[CrazyStat]

Anything that you use often enough can be memorized. A cup of flour is 120g, for example. But I use something like molasses maybe 5 times a year, so I'm not going to remember how much a cup of molasses weighs.

(I use molasses as an example because, due to how sticky it is, I much prefer to measure it directly into my mixing bowl by weight rather than using a liquid measuring cup).