Simply because they have no value, and you don't sell it anywhere. Some may sell but prices are too small for us to trade. So I think it's a reluctance to keep those altcoins in my wallet.
Even though we seen such small value on our shitcoin assets, that doesn't mean the end of everything, because there's always hope despite of recenta failures. No one can predict actually what other shit coins community planned for, and actually more projects been suppressed since bearish marker continues to happen. Most of the devs were waiting for the bull run to happen, until they decide to do pricr hypes which could boost up a crypto coin prices rising.