I do this drill - but with two gloves. It helps with maintaining pressure point #4 (left armpit) and pressure point #5 (right armpit).
Pressure Point #4 (PP4) is referenced in The Golfing Machine (TGM) - which is your left arm loading across your chest on the backswing...
Pressure Point #5 (PP5) is referenced by MORAD instructors - basically Mac O'Grady theory which took TGM concepts to another planet...
The benefits of maintaining PP4 and PP5 for me is ensuring my elbow spacing is tight - and helps me get the club/shaft loaded properly as I go from A4 (top of the backswing) into downsing - A5/A6/A7 (impact).
From my perspective... Having a solid PP4 helps you get your hands up, back, and in on the backswing... And then maintaining it on the downswing ensures you are down, forward and out. The glove should drop after you are midway through follow through.
Then the PP5... Helps with my right elbow placement and gets my right forearm takeaway on plane - and ensures the clubs sweet spot path is online in the downswing.
If any of you watch the Purestrike Five Simple Keys (5SK) videos... Basically this would be a drill which would help you with Key #4 which is sweet spot path.
In summary... It's a great drill and more golfers should use it.
EDIT: I'll add... For me, when I get quick with my tempo - or over swing - my right arm/elbow travels too far in the back swing - pulling away from my torso where I lose pressure under my right armpit... With my natural bowed wrist at the top (club face is closed) - I tend to over draw or hook the ball - especially with my longer clubs. So this drill, maintaining pressure under my armpits leads me to have tighter elbow spacing - which helps ensure that I don't over swing. This actually promoted more of a fade in my swing. And when I do this on the course - it basically eliminates any worry of a snap hook or over draw.