Because in the notebook character forms, they offer a place to write this down.
Personally, I don't like to do that for a few reasons. Maybe I'll write a small description, but never numbers. Here's why.
a) Most the time, irl, we don't know people's exact heights and weights, we just think, "Tall" "Small" "Thin" "Thiccc" ect.
b) I don't personally know a lot about height to weight ratios, (and that's then on me for being lazy lol), but it can be frustrating to figure out
c) I don't usually consider it important to my plots. This might be just a me thing, I keep my character descriptions vague on purpose in my stories, and if I'm not being to detailed about hair and skin, why would I be about height and weight?
But what about you? I see a LOT of people commenting about weights and heights on character critiques, and I'm wondering what other people think of them/why they write them down. I'm interested in your thoughts!