Some persons, don't intentionally sells off their investment like that,but due to situations they are forced to since they have good fraction of Bitcoin, they sells it off if they want to sell, some persons sell off their investment that they must have accumulated for a long-term period due to health issues because there is nobody to assist them financially for their medications, while some sell off because they are dieing and don't have any trusted person to transfer their inheritance to, and so they sell it off to fulfill their last wish if they have any, or eat up all their money before they die, so that the effort being made buying and accumulating their investment will not be a wasted effort
Agree with this because I have been in that situation before. But fortunately, I have emergency fund that I always prepare monthly just in case I have an urgent situation. So I don't sell too many satoshis but just help to cover the emergency funds if that funds can not cover it. It is why you need to allocate some money for emergency fund to cover your health issue or other urgent situation so you don't have to sell your Bitcoin. Until the time to sell is come, you will have your chance to enjoy your profit and prepare the funds for many things.
Many people do not understand the importance of an emergency fund at first, but when they face a real situation and need money, which forces them to sell their holdings at a loss, then they realize the real importance of an emergency fund. An emergency fund should be mandatory to sustain an investment in the long term, because unexpected situations naturally occur in a person's life, no one can ever say that he will never face unexpected situations, so a good emergency fund must be prepared with realistic thinking in mind. With a strong emergency fund, an investor never has to sell his holdings at a loss and he is able to hold his Bitcoin holdings for the long term.
It is not actually like people don't understand the importance of emergency funds they do actually but rather some folks or let me say traders chooses to buy with everything they have so that if there is any market uptrend they will make plenty profit which is wrong mindset because you can not actually tell if Bitcoin will pump immediately after exhausting your money. As an investor, I know one can not actually know or measure the emergency funds that will be good to handle any situation that may comes but at least have and keep if first because it is better than having emergency than not having at all and we all know what they means when challenges come up.