Your CMMS works in tickets, not signals. By the time something becomes a ticket, the line is already down or the engineer is already standing in front of it with a multimeter. The historian had the early warning two days ago. Nobody was watching the historian.
Most 'predictive maintenance' products are calendar-based or vendor-specific. They tell you when to replace a bearing on a press they sold you, not when the spindle on the line next to it is starting to behave like the one that seized in March. Plant engineers know the cross-asset patterns; the tools don't.
And the false-positive rate matters. Maintenance teams that get paged on every drift learn to ignore the pager. The question isn't 'is something changing?' — every signal is changing. The question is: is this change worth pulling someone off the line for?