The problem is that buying during the dip and selling on the ath is not as easy as it seems, a lot of people say that this is the best thing to do, but they do not even know how to do it..
It is difficult, and you are never going to be able to predict a new dip or just a new all time high.
It does not always workout either. I had lost a lot trying to do that in few alts and a few alts I HODL actually have gained more.