Not necessarily, it's staff flexibility, rather than have 'Check-out Operators', Shelf Replenishers' Warehouse Staff' etc. they now seem to have multi-task trained personnel - when they need more people on the check-out's they take people away from shelf filling and when it's quite there are more people filling the shelves IYSWIM.
You don't get in-store bakeries re-heating 'home
That's a bit unfair, most (if not all) don't market the bakery as 'Home made bread' etc. just as 'Freshly Baked'.
You don't
That is NOT the point of 'loyalty' cards, it's a cheap and highly effective way of market research and product marketing / placement (anyone ever get discount coupons for types of products they have never bought ?), they know were you live and what you buy - that gives marketing people reams of information for just a few pence rather than the pounds it would cost if done via the old style market research methods.
You can't
If there was not a demand for the other 95, or so, bottled waters the supermarket would not have them on their shelves - shelf space is expencive and products that don't sell simple don't get stocked in the store (even if it is stocked by the same store 5 miles down the road in the next town).