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.
Last time i check DCA and Lump sum is not in competition with each other. Both of them are good and preferred strategy to any investor. Do you know that Lump sum investing has outperformed DCA investing over 60% all time statically according to my research. Micro Strategy and other big tech firms are using Lump sum to buy and we get to see billions of dollars invested in Bitcoin. Same way people are much interested in DCA is the same way many are interested in Lump sum. Honestly, if an investors has enough capital and do not see any reason (risk tolerance, market fluctuation, low capital etc.) to DCA then he should Lump sum. DCA is usually a good strategy for those that don't have the capital upfront.
With of this being said. If after investing we are left with no money at all then Lump sum is not for such investor. We shouldn't invest in Bitcoin unless we have paid off all the high interest debt, cover all our monthly needs, have at least 3-6 months of fiat in an emergency fund to cover unexpected life expenses.
Lump-sum is simply not for those without upfront capital, lump sum is definitely for those who have a significant amount of money available and can invest it all at once without impacting their cash flow. It can be a powerful strategy if you're in a good financial position. Lump sum shouldn't be seen as a risky way to invest but rather as an aggressive way to invest in Bitcoin. It allows you to capitalise on potential market growth right away, especially if you are confident in the long term potentials of Bitcoin.
Know your capabilities during investment if you can lump-sum then it alright, but if you can't due limited capital DCA will be more suitable, by investing smaller amounts consistently. Understanding your financial capability and choosing the right strategy will help in your investment journey