The store manager said they only sold 10 bottles to each person so they weren't selling in bulk, which means all the bottles were loose on the shelves.
The store manager simply told them the purchase limit (on that exact product) in accordance with store policy.
It doesn't mean there isn't some type of bulk purchase option at the store for a similar item. For example:
My husband likes those Arizona green tea, canned tea's. There are two buying options at our local store. We can buy it in single 20 ounce cans (I think that is the size, but can't remember off hand) OR, I can buy it in a 12-pack case of 12 ounce cans.
The larger cans are .99 cents each
The 12-pack case of smaller cans is just under $3.50 for the case of 12.
The savings is in buying it in bulk and not in the single cans - by far.
For most items, especially drinks, there is always a bulk option. It may not be the exact same size, and sometimes your slightly more limited as to flavors (although not always) but there are always bulk options for purchasing in stores like Tesco ... and they usually save you a decent amount of money..
That is why I said the cart said it all.
No normal shopper will fill a cart with single bottles like that. If they need a lot of water they will automatically go for the bulk option in order to save money, and just buy a case or two.
Stores who put limits in place, are normally stores that have been hit hard by couponers and lost money due to those fake coupons.