You are missing something here, the the idea behind the DCA method was designed to meet the need of those investors who wants to owe bitcoin but don't have the money to finance their desired level of bitcoin holding at once. These are the low or medium class level of income earners who receive their money on a weekly or monthly basis. The DCA gave such investors the flexibility to own bitcoin without disrupting their daily financial needs in their lives. So if they are to buy at a fixed amount of money as they can afford let's say $50 or more weekly or monthly that will be okay with them. But if the idea was to be buying at fixed fraction of bitcoin weekly or monthly it will be difficult for them to meet up, and also it disrupt their other financial obligations in their lives.
How often do we see the dip? Mind you there is no general acceptable price level that is considered as dip. Dip is on individual satisfaction level.
Your making it would like DCA is a strategy that is used only by people without proper funds to buy bitcoin at once which is totally wrong, I can have enough funds to buy bitcoin and still decide to DCA because of the advantages it has over other strategies or preference, and we should not forget that we DCA to remove the panic and fear that comes with market volatility, not low budget, the only reason DCA has been said to be good for low income eaners is cause it allows them to split the total amount they should use to buy bitcoin at once into bits until they are able to aquire their desired bitcoin.
I can have up to 50k$ and I know I am fully able to purchase one whole bitcoin and decide to divide the money into 4 equal parts and buy Bitcoin, I can end up acquiring more bitcoin because of the volatility of the market and it becomes advantageous to me. And I also think another reason we prefer the DCA method is that, it supports holders more than any other strategy, cause if I had a dream to accumulate up to 10 bitcoins in 5 years and I had enough money to buy a whole bitcoin, i can chose to divide the money in parts and keep on buying in part so I could replenish the money and buy more, instead of just going for a lump sum at once.