As for me, it's not that surprising, considering that most people aren't that rich to afford various risky investments. Also, even if we take large investors - it takes nerve to see BTC drop in price and still keep it on the wallet, also, many people are greedy and they sell just as the price begins to drop.

So potential longtime holders are either very rich people who don't care if they lose money, but if they're rich and not interested in profit - why invest in the first place? Just for fun, I guess, so we can't expect the % of such people to be large. Or, it can be ordinary middle to upper-class people, but for this kind of people, it must be particularly hard to see their investments lose value as Bitcoin drops in price, so many of them eventually sell.