it's funny that some persons will wait for moments when they see bitcoin price going up before the thought to invest in bitcoin comes to there mind and like you rightly pointed out, bitcoin price can go up and then up, up and then down, down and then down and so on. so you can't just predict that because it is going up now , this is absolutely the time to invest into bitcoin and when you see the price going down you retreat from your plan on making the investment. It means that if you even successfully make the investment, you can't hodl your bitcoin because in the event of any fluctuation in price, you will let go of your investment.
Real investors sees the prospect of bitcoin and invest a certain amount and leave it for quality amount of time while he monitor the price without getting seriously moved by any fluctuations in price that comes along the way.
It's quite funny how some people apply their strategy in accumulating Bitcoin, in the first place why would I prefer to buy Bitcoin when the price is making its way to the top instead of purchasing when the price was much lower. When the price is lower I can make a bountiful profit than when the price is in the bull run, meanwhile there is very strong assurance that Bitcoin must surely make its way to the top.
It is right time we acquire some certain knowledge and apply them, everything goes with planning and strategies, we don't just wake up and decide to invest without studying what is involved in it.
It should be in our utmost plan that when the price is at the DIP or anything less than the last ATH it is a very good time to buy more even if a person is on DCA it still doesn't matter
The choice to buy is made based on an individual conviction and mindset, and not based on Bitcoin price, because the price you think is high may be a low price to the other person and for that, he prefers to buy at that price in other not to miss out of the present market sentiment, so bitcoin accumulation is a sentimental journey so for that, i won't make any assumption on why some bitcoin investors choose to buy more Bitcoin when the price is already making it way to the top, and no trend last forever so if the investor dims it fit to buy into Bitcoin at that price so be it.
But as a knowledgeable investor who may have had long-term experience in the market, it will be a wise DCA approach to accumulate more bitcoin only when the price is at the discounted level and to avoid DCA when the price is high because a high price should be best used for cashing out profits, and not to open any buy position.