Why aren't passengers instructed how to lift aisle armrests?

Only when I chanced on this /r/LifeProTips post, did I know

Most airplane aisle seats have a small lever or button on the underside of the armrest, near the hinge. Pushing or sliding this lever will release the hinge lock, allowing you to raise the armrest.

When horizontal and down, aisle armrests obviously hinders exit during emergencies when saving seconds can save lives, especially for more obese passengers. So why isn't this hidden button/lever disclosed to passengers, like in the mandatory safety briefing or video?

I'm not asking about armrests between seats that don't require a hidden switch to lift.

• easier seating of those with limited mobility Would that not include easier exit of those with reduced mobility? This one never made sense to me either. The better reaction would be to simply make sure the armrests are designed so that they don’t protrude backwards when stowed. The ones in between seats don’t. – TomMcW Feb 23 '19 at 17:44