Too Long; Didn't Read
While centralized exchanges may be convenient for users to store their crypto holdings if anything were to happen to the exchange, there's no guarantee that anyone can get their funds back. This is why it is often recommended for users to store their crypto using a wallet that gives them access to the seed phrase and private key. Centralized exchanges control the private keys for a user's funds, so when they go down or get hacked, there is no way for a user to retrieve their funds.