Because when new bull run will arrive there will be new shitcoins and your shitcoins will end dead or delisted from exchanges which can lead to 100% loss.History is always repeating.
5,5 years old chart:

Surprisingly some coins from this chart are up from then but volume on exchanges is low,so holders of these coins are truly bagholders.
I think you are thinking of sh*tcoins in a different perspective or definition. As shown in the chart, those coins still exist, even low in price and volume but they did still exist to the fact they are only copying bitcoin in the first place. "Sh*tcoins" this time serves their whitepaper using blockchain to be applied in real life, still developing, so you really can't tell. Maybe one day, that "Sh*tcoin" you're hodling is the next ether, who knows?