Team Green (Only)

I’m curious to know this (without judgment at all) but I always wanted to know what makes parent(s) wait until the baby gets here to know the sex of the baby and is it hard going 9 months without knowing?? I ask this because I’m such a impatient person lol and I like to prepare... I know people buy neutral colors but someone like me has to buy either all girly or all boyish things lol I admire you guys strength.