In sideways, trading is possibly the only way to make money. Pumpin and dumping takes place is every market, especially in accumulation phase. So of course you must cash out from time to time. Holding everything in crypto is potentially very profitable but also very dangerous, especially if you relying on low-cap coins. They tend to fluctuate very much. Coins from top-5 are safer, but we also witnessed numerous ups and downs.
You said everything very correctly, yes, because there is a person who is not worried about his household budget and has the means to pay any bills, and also if he has an additional source of income, then of course you can save all cryptocurrency capital in the cryptocurrency market and not cash out . But in a different situation you need to live for some money and therefore you have to cash out.