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.
In short, monthly/weekly/daily DCA each has its own advantages and disadvantages, and depending on each person's circumstances, there will be a suitable choice. We should not impose our thoughts on others when we are not in each other's shoes.
I agree that it is better to buy bitcoin outright and hold it for the long term than to buy it every day as the risk is lower. It is true that centralized exchanges can be hacked which means there is a risk of losing your bitcoin also some exchanges may have higher transaction fees which can increase the total cost of following a regular DCA. If you plan on DCA every day using a centralized exchange can be risky. Therefore it is best to use a secure hardware wallet or cold wallet to store bitcoin for the long term rather than keeping it on an exchange.