I also get the point that you are making transaction fee can be very expensive if you add them up together, but let’s also not forget that some people who choose to be making their purchase on a daily basis DCA daily some of them use centralized service to do that they buy on the exchange leave the coins their daily which they don’t need to spend fee until they accumulate up to a certain amount where they can then withdraw and pay only one time transaction fee.
Daily DCA plus using centralized exchanges to store bitcoin will save you transaction fees but you are risking your assets. There is no guarantee that those centralized exchanges won't get hacked or that your account won't get frozen before you withdraw bitcoins to a non-custodial wallet. We should not put ourselves in danger, so I also do not support the idea of daily DCA and using CEX to temporarily store bitcoins.
I understand the danger you are talking about and how it feels of trying to reduce how much fee you spend eventually put your funds in danger, it was just an example which I gave which no matter how you advise some people they can never stop using centralized exchange and beside you can never be too careful just that moment between when you decide to buy and withdraw anything can happen it’s almost same thing as buying and leaving for couple of days before getting it out to noncustodial wallet, I don’t know if you understand the point I’m making.