Why do restaurants usually boil noodles in water and then put them in broth?

This involves a waste problem, because when cooking noodles, no matter what noodles are cooked, there will always be some surface ash. The more noodles you cook, the more ash in the pot, and the more ash in the pot. So if you cook noodles with broth, it's a waste. If you can't cook a few bowls of noodles, the umami flavor of the broth will be destroyed by these dissolved flour, which will not only make the taste strange, but also make the soup turbid. Noodles cooked in water no longer have strong water absorption. When put in the broth, noodles do not absorb water, so the broth has higher utilization rate and higher income.