Because market of crypto can not be predicted.
No ones knows flthe future of it, and we all have seen the journey of the market since the last pf 2017 till thr middle of 2018, it run fast.
And the wave was so far, the market is getting crazy day by day.
No wonder if mny people afraid of investing in crypto.
Yes because it will be hard to predict and the fluctuations are mostly in deep range, then some people think that this can be categorized as gambling. That is one of the reason why people don't invest in crypto from my own assumption.