Lots of people are saying that cryptocurrenices aren't a good investment because just hoarding the coins over time they will lose their value. I disagree. Not everyone is going to be hoarding for a start. If the currency has great features, potential and relatively cheap say 2 cents a coin just starting. In 3 years time it that coin became worth say 3 dollars and you decided to sell, you have made 150x what you invested. Am I missing the point here? Maybe there not good investments in the traditional sense More gambles. But still a gamble like that would of paid off so maybe it's not such a bad idea taking somewhat of a punt.
You are right that one can earn a lot if buys a coin for a couple of cents and sells it for a few dollars. But that is what others call 'no value', for thus we treat cryptos as means of earning money and nothing more. Thus, once everyone decides to sell, because they have always waited for a good time to sell, the coins crushed.
However, I would add that some coins like btc and eth are starting to get their material backup by being implemented in business projects. And this can truly save them.