It's hard to ignore how handy it is when someone else holds your money. When my bank holds my money I can send it to anywhere from any place. Using a crypto wallet I now have this file I have to somehow keep safe and with me at all times. What happens when or if it gets stolen? Like cash it's gone.
So I understand why people do it. Ease of use typically outshines most security issues. Someone needs to figure out how to strike a better balance.
I still haven't convinced my own brother that he needs to move his coins off-market - he said he'll "get around to it at some point"
Also have tech friends who keep coins in Coinbase/Coinbase Vault