When you buy digital currencies through a centralized crypto
exchange, you will have no control over your private keys. A
centralized crypto exchange will store a percentage of your
private keys in a hot wallet, while the rest will be stored
in a cold wallet. Centralized crypto exchanges are the main
target of unscrupulous hackers because they concentrate
large amounts of wealth in one place. In the past, crypto
exchanges like Mt. Gox, Quadriga, or EXMO were hacked
leaving many investors with big losses on their investments.
This is one reason why you should have control over your
private keys, so you can store them safely in cold storage
wallets or also called hardware wallets.