From what I read, someone who sells btc sometimes has trouble receiving the fiats in its bank account. If the sum is large, the bank turns on all its red lights.
This is the problem with fiat currencies and their centralized censorship institutions, they want to regulate you and your money, they can also confiscate your money because they control it. The banks usually get suspicious when a huge sum of money enters your bank account, they want to know the source or origin and they can freeze your funds. There are two things to do in this situation: it is either you convert it all get ready to prove that everything you do is legal or you leave your funds in the BTC network that is censorship resistant and permissionless and convert to fiat after every two weeks or more, so the withdrawal process would take a long time and may not raise any suspicion.