I believe the concept of HODLing Bitcoin is nearly as old as Bitcoin itself with the fundamental reason and hope that it will increase more in value over the years. Although several persons are entitled to there own reasons for HODLing, could it be that some persons HODL because they are waiting for the perfect time or they are too scared to sell or lose a percentage of their Bitcoin?
There is no other reason to hold bitcoin other than making profits in the long run. Holding bitcoin doesn't mean being scared to sell, there is a season to hold and a different season that is appropriate for an investor to sell. It comes in a bear season where investors are intrigued to buy more, while the bullish season that comes after a bear season, is the season for investors to sell. Any investor that sell during the bearish season is doing the wrong thing, we hold bitcoin so to make maximum profits not cause we scared.