If I (or any boarder) want/need something done for with our horses (blanketing, leaving in/out, etc) the barn owners are happy to help. All it takes is a note on the board.
Ahh... but see you can't compare barns because what is provided at a barn is tied into how much the individual is paying and the contract they have.
If I wanted to pay a small fortune, my trainer would be more than happy to do whatever I wanted, even sing my horse lullabies at night if I so wished. I don't, so she provides the care outlined in my contract which includes blanketing at HER discretion. If she feels he needs a sheet, blanket, fly mask or whatever, she puts it on/off. Otherwise he goes without or I can drive over and do whatever I'd like. I trust her judgment, so my boarding arrangement and what I pay is suitable for me.
I can't pay bargain basement prices and expect blanketing, hand walking, nighty-night lullabies and the like. I could wallpaper my horse's stall with notes demanding all sorts of services and all that would get me is an e-mail or phone call to inform me I was a dolt and not getting them unless I wanted to pay for each one.
If blanketing is not specific in your contract and you aren't paying for it, you cannot realistically expect it, no matter how large a note you leave.
And, as a boarder, I wouldn't touch another person's horse. Warm to my horse isn't warm to a different horse that shivers if they think the wind might blow. Not to mention, if I don't know anything about someone's horse, the last thing I would do is go into a stall and try to remove a blanket. What if the horse is completely and utterly terrified of flappy blankets being pulled off!!?? I value my safety and a horse being mildly uncomfortable with a blanket on is better than me being kicked or bitten for trying to take it off.