It can be difficult for Bitcoin and cryptocurrency investors when they hear about it the first time and they have yet lost money by any centralized exchange by either of following reasons: scam exit, exchange hack, exchange death, exchange bankruptcy.

When they experienced it with their own capital, lost their capital, they will no longer see that using a self-custodial (non-custodial) wallet is too difficult in practice.

The challenge is whether they see it is important for their fund safety, and whenever they see this importance, they will learn and use non custodial wallets (also need to be open source) for storing their bitcoin and cryptocurrency.