Someone in my family works for a supermarket, so family loyalty comes into it as far as my shopping goes.
The Loyalty card rewards are a handy extra, but I think those days are numbered - food retailing is changing, and customers are being influenced far more by straightforward value for money than by bells and whistles.
The wife does most of her shopping at Tesco but will admit it is not the cheapest just the most convenient for her. Parking, quality and range of goods etc. also come in to it. When I used to do the shopping I went to a local supermarket known as Kwik Save just because it was the least expensive. Kwik Save has now closed and there is an Aldi in it's place so I would probably go there for my shopping.