I totally agree that it is not the best profitable thing to just buy and hold, after all there is more money to be made by volatility than stable income. However you are forgetting that not everyone can make that much money that quickly, they are not traders and that is why they could also lose a lot more money as well.
The difference between trying to make more profit with trading versus trying to make some money with long term holding is the simple fact that when you are holding you will eventually profit and that is the end of it, but when you are trading you could end up losing money. So, one has a potential to make a lot more profit, but also has a potential to lose money as well, while the other one has very little chance to lose money but also has huge chance to make little profit.
Trading is basically gambling and like most forms of gambling, the only winner long-term is the house. The individual retail punters will break even against each other but it's the vigorish that keeps the casino, racetrack, bookie, or lottery corporation in business, while eventually making losers of everyone else.
In the case of Bitcoin, it's the exchanges and money transfer services (or ATM operators) who take the profits. The only way to avoid this is to mine your coins or buy them OTC without fees, and spend them or sell them also OTC without fees.
Buying and selling coins according to their current price (trading) is nearly impossible without paying fees regularly. This is why long-term holding is so much more profitable than retail trading.
Professionals with sufficient resources to manipulate the market are a whole different story. If you can afford to lose a few million dollars (by dumping a load of coins) to crash the price and make much more on heavily leveraged shorts at other exchanges, of course there's money to be made. Obviously that money has to come from somewhere. Well hello small-fry traders!
Trading is for suckers.