Nothing is flawless in this world. The way custodial exchange are beneficial for the traders, in a similar way, non-custodial exchanges have their own loopholes. Probably, it will be perfected over a period of time but right at this moment it's difficult to operate even for a seasoned trader. The user-experiace needs to be simplified first to get attention of the mass. The matter of fact, the usage of non-custodial exchange is shrinking. Read below,

https://www.theblockcrypto.com/linked/52698/total-volume-on-non-custodial-crypto-exchanges-hit-9-month-low-in-december

Not really sure what will happen in future. But at this moment, non-custodial exchanges have not been able to become an worthy competitor of custodial exchanges!