Corruption is most of the time not such a big deal. As much as how not defragging your win98 instance wasn't really a big deal either.
Until the thing blows up.
It simply could cause bigger issues, which leads to potential data loss when it could have been prevented.
Run an optimize and repair a few times. And yes, that will report back some tables as up to date, some as unable to check or optimize, and some simply don't support the type of action because they're like a session table, or simply stored in memory for other reasons.