Because the DCA strategy reduces the price volatility to some extent.
Even if one makes use of DCA Strategy the price of Bitcoin will still keep going up and down after you buy. So I would say this-]DCA Strategy doesn't "stop" rather does it even "reduce" volatility.
What we can say that DCA Strategy does is that it helps spread your buys so you don’t risk putting all your money in at the worst timeNo, I disagree on this your highlighted statement here buddy, the very purpose of dca accumulating strategy is to make accumulation of Bitcoin very easy and affordable even for the poor, because you can be buying it bit by bit according to your financial strength, and point of correction, their is no worst time to buy Bitcoin, because it's still very cheap when compared to how much the value can rise up to in the future, so what you said in the highlighted words are false.
Additionally, volatility is part of the nature of Bitcoin, so it wouldn't go away all of a sudden because you are accumulating through the dca strategy.
You are right there is nothing as putting all your money at the worst time because those that have a larger amount to lump sum can do that without considering the market conditions, that DCA is a good strategy doesn't make other strategies in effective when it is used appropriately, people can lump sum and even front load their investment if only they have the capacity to do it without having a negative effect on their area of life, it is now obvious that there is no worst time of buying Bitcoin because the market is unpredictable.