Well, I did get to groom Darcy after my lesson today :) Ended up covered in white and brown hairs and bits of mud and horsepoo (got it all over me when picking out his feet) but it was lovely and relaxing. He was touching my bum with his nose while I was doing his front legs xD Unfortunately the horses usually stay tacked up for another lesson, so I don't get to do that.
Thought of another advantage, though! Pro:
when you have no idea what the hell to do, or something is getting too difficult, you can get a groom to show you and then they can do the hard stuff.