In a crypto world were there are no 'banks' that will insure assets are safe and cover any losses, it is paramount that crypto owners take care of their assets.
The cold storage idea is a good one, but when left to a centralised facility the risk lays in that facility being able to keep the keys to stored values safe. If their servers are not offline, airgaped and many other techniques then those keys are vulnerable to outside attack.
After seeing the abilities of some to break even the most secure security like happened with stux-net and Iran, putting trust in others is false security.
When safe guarded ourselves, we still need to deal with lost mobile phones, computer viruses and other issues.
This is an area that has yet to be addressed by the industry in a perfect and secure way.
Which lead back to creation of paper wallets stored in a fire proof safe as perhaps being the most secure way atm.
https://www.newsbtc.com/2019/01/31/crypto-exchange-quadrigacx/