This is the explanation why there are people never profiting, while others are making huge money. I am gloating with the anticipitation of the next bull run when all these noobs will bite their tongues for selling at 4K, while the price goes above 40K! Mark my words!
There are also another reason people sell at those prices though, and that's margin-calls for people who trade BTC in margin. I don't know why would anyone do that... margin trading in an already high volatility market makes no sense to me! It's probably only addicted gamblers who do that.
But there are such services and if they exist, it means that some people use them.
Unfortunately that's another reason for the market makers to drop the prices, trigger the margin-calls of people who though that the price would NEVER drop after a certain level, and grab their money.
That tactic is hard and expensive to perform in the usual Forex market with fiat-currency trading and shares, but in a low liquidity market where whales exist, it's theoretically still easy to manipulate the market. I'd give it at least another 2 years before the wealth of BTC is more evenly shared and the price is less prone to manipulation and sharp movements.