I regularly buy flowers from supermarkets and have never had any with a bag of water. They do usually come with a sachet of flower feed, but that's all. In any case, a little bag of water would only be intended to keep them going until they reach their destination - not for permanent display!
I still say leaving the paper on is ugly and pointless, and I'm pleased to see that the bench flowers are shortly to be removed and turned into pot pourri.
As an aside, a tragic event in a town near me was marked by people tying coloured ribbons to trees and lamp posts around the town. Somebody started it, and it caught on. It was rather lovely, and lasted much longer than flowers.