Bitcoins are a long-term investment with a good profit, I do not see the point, to sell, what makes a profit. If it was not profitable and did not bring joy, then yes, and so the price of bitcoin only grows. But maybe you have other reasons for this.
The main purpose to introduce bitcoin was for investment like gold and here you are right that one will get huge profit if he/she invest it for long term but some times we see that other commodities have better value and more beneficial profit option than gold. So one may covert his/her bitcoin to other commodities for better return. Converting it to fiat for no reason is perhaps a lose.