DCA (Dollar Cost Averaging) is one of the most effective strategies for investing, so this effective strategy is used by everyone from wealthy investors to those with relatively little money. It is different for those who don't know about DCA investment till now but those who know about DCA investment strategy should definitely invest in DCA strategy instead of investing in other strategies.
You are correct that the DCA strategy is the most-used strategy in bitcoin investment, but that doesn't mean if you use other strategies in accumulating bitcoin, you won't be successful in your bitcoin investment. As far as bitcoin investment is concerned, if you are using the DCA strategy, the lump sum strategy, and the buying the dip strategy, if you have a steady income and invest in bitcoin with your discretionary income or invest in a way that you will not always struggle to sort out you daily expenses, you will surely succeed in your bitcoin investment because you will not depend on your bitcoin investment to survive. The reason the DCA strategy is mostly adopted by the rich and poor folks is because it allows them to consistently accumulate bitcoin in both the bullish and bearish states whenever their money is readily available, and the DCA strategy also helps to control investors emotions so they will not think of buying bitcoin at a high price.