CBM replaces "replace it every 6 months" with "replace it when the data says it needs replacing" — a bearing running cool and quiet at month 8 stays in service; one trending hot at month 3 gets flagged early. It requires sensors or telemetry the PM calendar alone doesn't need.
For assets where condition genuinely varies a lot between units under identical schedules — motors under uneven load, shuttles cycling at different rates — CBM catches problems fixed-interval PM misses entirely, because two assets on the same PM schedule can be wearing at completely different rates.