It is clear that for you cryptocurrency is only about profit. If you are willing to trust a 3rd party with your keys for 8% interest (if that even exists) maybe you don't have much invested or you are just naive. What exactly do you think was the vision of Satoshi Nakamoto when he created Bitcoin? Do you think centralized exchanges follow that vision?

More and more people are moving away from banks to cryptocurrency in general precisely to be able to remove the 3rd party. To take some responsibility and control their finances. It is difficult obviously and things can go bad if you lose your keys but is a risk some of us are willing to take, and you have to have some backups and with time people will develop better ways of securing their keys.

If you are using an exchange to trade constantly that's understandable but if you are using them to store all your funds or a huge part of it, that's just dumb. With what you are suggesting, just keep your funds in your bank! The only downside is you won't have 8% interest annually but if your concern is security a bank is more secure. Centralized exchanges have all the downsides of banks but in steroids! No privacy, security meh, prone to hacks and no refunds, fishy staff, withdrawal limitations, locking accounts and I could go on an on, I mean just check the news and every once in a while there will be exchanges hacks... Just take some responsibility and assume your finances, that's the purpose of cryptocurrency.