People usually do this due to panic that a certain investment would suddenly become valued at 0 which is a total loss for the said investors. Ultimately, if an investor is scared of such a scenario, they would cut their losses, but smarter investors just average down their assets to prevent further losses and to also make room for possible profit amidst of deep losses.
Most of the people affected by such a sentiment are those who just joined the fad without studying it thoroughly.
I agree with most of what you said and summarized parts of this strategy in this post:
https://medium.com/@robjeiter/what-the-mainstream-media-doesnt-tell-you-it-is-rational-to-invest-in-cryptocurrencies-3f7892173eea