I always used to use that as an argument until I spoke to someone 'high up' in a bottling plant.
The reason they have to date it is because all types of plastic leech impurities into the water. When I suggested using glass bottles, which are multiple re-cyclable, his reply was the consumer wouldn't pay the increased cost of glass over plastic and most people would throw them in the bin anyway. Wouldn't listen when I suggested putting a deposit on the bottles which you would get back when you hand them in. Said it would never work.
Mind you, he was only in his late 30's/early 40's LOL