Different people have different strategies in terms of investment and everybody have a particular strategy that work for them.
Buying Bitcoin by DCA does not necessary mean that the investor have limited capital, most people that buy Bitcoin by DCA still have the capital for lump sum but one of the reason why some people prefer DCA to lump sum is that some people see lump sum as a method that is risky because of the volatile nature of Bitcoin which they cannot possible tell what the price may be in the future. So to avoid any uncertainty in regard to dip they see DCA as precautionary way of buying Bitcoin than lump sum which requires buying Bitcoin at once with the capital at hand without considering whether the price will dip or not.
The truth is that if an investor see's lump very risky because of the volatility of bitcoin I don't think the DCA method of investing will be seen in a different way because these are different strategies of investing but the same market. I do not agree with you why you think people don't prefer lump strategies because of the volatility of bitcoin, even in the DCA method volatility still happens. People just prefer to use DCA because it is straightforward and stress free. The most important aspect using the DCA method to invest is that you can be very consistent with your investment because you are just investing with amount you can afford, it doesn't matter what the amount is but the important thing is that one is investing with ease.
Majority of investors prefer the DCA over the lump sum because it offers more good features, not waiting too long to gather capital before investing at once and it helps maximize profits. The DCA is very reliable for both the shrimps and whales, the shrimps don't need to wait for long to gather enough capital to invest at once but can invest in bits on different intervals, according to how their income permits them. For instance, big companies like BlackRock and MicroStrategy are capable of buying bulk bitcoin at once and hold for long-term (lump sum) but not every can do that and that's where the DCA plays a good role, like i said earlier, it offers not just shrimps but all class of investors the opportunity to buy Bitcoin in bits at different intervals, meaning that those who can't afford to buy bulk BTC at once or wait for a long period to gather capital and miss out on different accumulation opportunities would have the chances of accumulating as well through the DCA and maximize their profits and also recover loses during the dip periods. The DCA is a very reliable strategy for all classes of investors and that's why it's vastly preferred by Majority of investors compared to other strategies. However, that doesn't mean that other strategies are not useful too.