On an exchange or bank, your cryptos do not belong to you. You risk losing them.
The exchanges or banks used to acquire your cryptos can go bankrupt: you would then lose your cryptos. They can also be stolen by allowing access to your exchange or bank to unauthorized third parties. The only way to really own your XRP is to transfer them to the blockchain and have the keys. To do this, you need to have a digital wallet secured by a Ledger with 24 confidential passwords generated by the Ledger.