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?
Investor Holding their bitcoin is for several reasons and part of it is that they are not ready to sell In loss and probably are hoping that by holding for the long run, the value of bitcoin will continue to increase which will in the process help to place them in a greater profit.
Being scared to sell is not entirely a bad thing as long as you're doing so to protect yourself. If you sell too early, you're going to end up being at loss. The future might seems uncertain but yet, it's still safer holding your coin for the future than selling it too soon because of fear.