When you are transferring in fiat currencies, the bank will always want to know the reason why you want that transaction to be accomplished. When you are sending Bitcoin from an exchange to another exchange, the exchange you are using might ask you for a reason or ask for strict KYC verification if you are sending huge amounts.

If you are sending from a wallet you have access to the key, you don't need a reason to do that. You can send as much as you want without giving anyone a reason. I'm up for corrections!