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.
Mnah and do you know more about these coins? They are just copy paste of Bitcoin´s open-source code. They are not diffrent, they are not interesting.
But now, look at altcoins, most of them are totally diffrent, diffrent use, diffrent blokchain, diffrent end users.