cryptocurrency activities are not stereotyped.
some will see reasons to sell, while others will see alternative reasons to buy.

For instance;
You saw a viable coin that you believe will appreciate in value on the short run.
That's one signal that the coins in your possessions are not showing; what do you do?

sell off the one in your possession for the viable option.

Other people may sell for varying reasons like FUD; etc. One thing is for sure; there will always be some people selling while others are buying. That's what makes cryptocurrency and exchanges unique.