Why do they flush first?

Why do so many users of women’s public or semipublic bathrooms walk into a stall and flush before they use the toilet?

I have been observing this for years and noticed that it is mostly Asian women who do this. It happens even in well-maintained office buildings that they work in and where they use the facilities many times a day, where there is no reason to suppose things aren’t working right.

What is the reason? What is the purpose? Why waste the water? Even if there were a little particle of paper or something left in the bowl by the previous user (all the time?really?), it’s not like you’re going to touch it. So why flush first?

Do they do this at home?