That they are going for pubs in some places probably says more about the sort of commercial property available to them at the right prices for conversion into a convenience store and maybe local licensing issues?
Round here its old banks and other similar commercial premises that are the sought-after sites for convenience stores and occasionally the odd pub club.
The one pub here that has been converted to a Sainsbury Local, despite its olde-worlde styling was actually converted in the late 80s from a religious bookshop that had previously been occupying the former site of one of the very first supermarkets in area - Low's, world famous as the source of our Typhoid outbreak. So I hope what goes around doesn't come around again! I wonder if anyone told Sainsbury?