Possibly the cause is that it is not easy to sell them. Let's be honest, who in her sane mind is going to give away good, valuable bitcoins in order to buy that shit? I am surprised that there is some market at all for those scamcoins.
To be honest? I AM!!!
I hereby openly offer 400sat for each and every one of those shitcoins! So Terk, be the hero to your miners once more, sell them directly to me! Make your miners the profit you promised them!