most of the reasons why these coins can be called shitcoins are because they are worthless, only listed on small exchanges, or even failed to be listed on any exchange, so they can't be sold and are worthless
that's mostly the right reason. cheap value even though they are listed on the exchange they have no real trading volume. especially those who only exist in the wallet and can never be traded.
don't you also have a lot of coins like that in your wallet?