Being rejected from a coinjoin is completely harmless to the user, they can simply register with a different coordinator with absolutely no consequences whatsoever.
Being rejected from a coinjoin means being rejected from protecting your privacy, which is rather the opposite of harmless. You are harming the people who might have not done anything and whose coins are arbitrarily subjected to crime by denying to anonymize their coins. Sure, they can go and try out in another software, as JoinMarket, but you do harm the reputation of Bitcoin privacy software.
As for the "simply register with a different coordinator", how is that going? Is there even one that is running separately from zkSNACKs?