Because those just starting out in investing generally only know that buying when prices drop is a good way to invest, this is similar to the Lump Sum strategy, which requires waiting for the price to drop before making a purchase, a common practice when first starting out.
It is newbie investors that lacks knowledge and experience that will adopt this strategy, waiting for the perfect dip before they buy. When they eventually gain knowledge about the best strategy to accumulate Bitcoin on the long term they will know that DCA method is the best. Bitcoin newbie investors needs to know that Bitcoin is volatile and they don't know when their targeted dip will happen, why wait when Bitcoin will always rally and reach ATH.
Whether it's using DCA method to accumulate through your discretionary funds when your income drops, don't wait buy immediately. If you're using lump sum to buy when you're paid for a contract, gifted money or inheritance buy it when the fund is available no matter the current price.