Some investors are generally interested in buying more BTC at DIP prices and tend to sell during bullish times. But holding is more important because it will happen again and again when ATH is observed in the market with gap of few months. A bullish period is characterized by overall market optimism and expectations of higher performance for the future. Even offers higher returns than bearish ones. A bull market usually reflects the utmost confidence of investors that a person can align their investments in this positive trend. Increasing market value makes investors optimistic about the positive loop. These positive market conditions may prevent investors from being psychologically tempted to sell BTC. It can even discourage selling during market downturns. Many investment firms can build potential wealth by investing more during periods of BTC price appreciation.
There is nothing wrong with someone buying an asset when the market dips and then selling it when the market is bullish even if the market manages to go higher than where they sell their assets because they have at least earned some profit on their investments, that's the main purpose and if it's achieved, it's all good.
Bitcoin in general is considered to be a long-term investment asset because it has a cyclical movement pattern where it tends to reach the peak at the end of the cycle and goes down at the beginning of a new cycle, and people know that if they hold, they can gain higher profits, but there is also nothing wrong in buying and selling multiple times during a full cycle.
If you're giving the opportunity to take small profit for 2-month investment or take a very huge profit for a 1-year investment which, would you prefer? Of course you will choose the big profit, and that is why people see the idea of selling Bitcoin when there is a short increase in the price of Bitcoin as a bad idea. Only hungry or hasty investors are willing to take quick gains, if one wants to rich and wealthy then investing a lot in Bitcoin and holding it for long so that the return will be massive will be their ultimate goal.