Why to eat the cream while you can have a cake after the cake is finished?
Profit takers will be buying again later to get even more cake. Of course, it's possible that they'll never get a chance to buy cheaper (e.g. bitcoin profit takers who sold at $1).
Do not get me wrong, I am doing this also...
I have separate investment portfolio and trading portfolio.
Trading I am doing to get something to do which gives me also a little bit excitement. Investments I hold for long haul and am planning to sell if I need to purchase something bigger assuming the price goes as I wish.
Trading however is the gambling side of me and I am controlling it not to trade too much. If Monero goes viral, there are pretty high chance that at some point it is impossible to get Moneros even sub 100 usd levels and if my trading position is in other currencies, I have lost the opportunity cost of having the appreciating Moneros.