The newbies have limited understanding as regards to DEX wallet which you will have control of the private. A newbie that recklessly lose his/her seed phrase and private key might not be able to retrieve his/her coin from this DEX wallet. However, CEX platform like coinbase is very easy to use and it is very easy to recover your coin in case you cannot remember their login detail
first of all DEX decentralized exchange. there is no DEX wallet, there are desktop wallets, cold storage, custodial wallets, hardware wallets, web wallets,...
secondly if someone who is incapable of holding on to their desktop wallet they are also incapable of holding on to their login information to a centralized account on some exchange and will lose it all the same.
besides if they want to give up their control and use a custodial wallet then they should continue using fiat instead of bothering with bitcoin.