Yes you are right, people may sell their bitcoin in less value time because may be they think that its price will go more down and will have to face more loss. So they sell them in less value and don't wait for the price rise. But it is profitable to hold the bitcoin when the value is less.
Selling the BTC or not selling it, well no one could take someone's decisions but we have to faced the fact that here is we talk about fiat so keep in mind that we're just spending money. I think it is not bad to sell bitcoin if it is in higher price or just keep holding it when it is in lower value.