First, some investors have investment worth millions of dollars into the market. Not to mention, some investors are also the ones who have slight knowledge about cryptocurrencies in general since they only follow the hype caused by media.
Second, complaining is inevitable once their seems to be a market disruption caused by various factors, such as whales manipulating the prices, country announcements that prohibiting the usage of such, etc.; and
Third, most people that complain are the ones that have unsound mind on what is going on. The truth is, people who complain are also the ones who say that they should have invested when the prices were low and when its price suddenly skyrocketed.
Well, of course, many people will complain that if the price of Bitcoin decreases, it is better not to jump if not ready to loss. Lol, every investor may want an increase, it's because they expect to get a profit, not a loss.
I disagree. Investors who know that price drops are a typical scenario in the cryptocurrency world should know that. Rather than complaining, they take this as an opportunity to acquire more for future investments. People who generally complain about price drops are the ones who does not know the process involved in cryptocurrencies.
and Secondly, People who just make their money in the market with swing trading and earning with small factors which provide them an income which cannot be figured because it depends on the market's outcome of where it stands. these are the few of the reasons of people complaining when the market is down. 
