They exist for other reasons. Greys are primarily for foreign issuers and microcaps who do not fulfill particular requirements for listing on a exchange, or brand-new issuers who have not yet uplisted to an exchange. They do not exist solely as a dumping ground for delisted, scammy companies, although they fill that purpose too.
As for delisted, scammy companies, there's no guarantee that they will even trade on the greys.
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