There are often contractual disputes which prevent a record getting distributed at the last moment or 'pulled'. Or the preceding record becomes a big hit so the company puts all their efforts into promoting that. Or it just doesn't get the airplay they'd hoped for. Or the Promotional / A&R men don't distribute them and they get binned instead. Or the artist has signed somewhere else by the time the record comes out. Or the thing was never going to get properly promoted, but it came as part of a job lot (e.g. three groups on a deal to get a record out on a label and despite putting it out the company never gets behind the third one). Or there's a fault on the pressing (could even include mis-spelling or omitted names)...many reasons, even for larger labels.