Panic sell is big loss for the ones who own lots of bitcoin or other currency, it's much logical to sell little by little with sell walls. Instead of dumping the market and selling half of the coins for half price, also crashing the market..
What it happens is that people do not have a strategy when it comes to their bitcoin, having lots of money does not mean that you know how to manage it, selling for a price lower than the one you bought is a terrible mistake, it is better to hold, even if you have to do it for years since losing time is better than to lose money.