I think there are people who would sell some of their bitcoin for the sake of taking small profit. It would not affect its portfolio that much if what he is taking is only profit but not a part of his initial capital. I,myself would take small profit because I want to enjoy my profit from time to time. With cryptocurrencies being so volatile, we never know what the future will be so taking part of profit is a safe way of diversifying my investments as well so that I will have more income generating business/investment aside from cryptocurrencies.