The absolute nature of the scale isn't THAT important, yeah it gives you an idea of how the pain feels, but what's more important is how the number changes over time.

If a patient keeps saying "IT'S AN 11!!" for an hour and then now it's a 9? Great, we're moving in the right direction.

If someone starts out saying it's an 11 and suddenly it's a 15? Well, what changed? Did some meds wear off? Did they shift and move something that increased the pain?

Heck, 90% of the time if I get there and it's an 11, then just 10 minutes later it's suddenly a 6 cause they've calmed down now that help is there.