You are right that you lose nothing unless you sell bitcoin at a loss. But many people invest the money they might need at any time. That is, money that cannot be risked. Cryptocurrencies are attractive because it creates the illusion that you can get rich quick just by buying coins. But when the market starts to fall, most sell at a loss.
That's called a wrong investment strategy, there are no cases of loss when people know the best way to invest, buying and holding bitcoins until they reach the desired target is the best way to achieve profits, if after the buying process the market has decreased, then it's just a matter of waiting for the next price increase.
That's why many people say bitcoin is the best asset for the long term and losses depend on how one understands the market, unless people invest in other coins and it's hard to see the same moment as often happens in bitcoin. Basically investing in bitcoin is very easy, but many people misunderstand market conditions and are not used to falling prices, so in these conditions they try to make the wrong decisions.