Far be it for me to disagree with our resident architect, but it's got very little to to with the individual planning departments, who don't really have a lot of power however lame their brains, and everything to do with national planning (and other) policy (why do you think local planners are even allowed to approve out-of-town supermarkets?), and beyond that with economic globalization.
The agro-food system, for example meat, is a case in point: a lack of local abbatoirs (they can't afford the regulatory and inspection fees anymore), means it is very difficult for small farms to supply local butchers now. This, combined with the purchasing power and economies of scale of massive supermarket chains, and the alienation of people from food production - the cultural aversion to seeing meat as it really is - has killed many local butchers.
Local shops can only survive, either if like Kirstie's they can do everything conveniently and are thoroughly embedded in the community, or if they are niche-market specialists, or are supported by a wealthy local middle-class. It is, unfortunately, everyday suppliers for the lower-middle and working classes that are being killed...