probably lots of people would like a single hole mixer but don't fancy their chances of invisibly filling the spare hole. SO! Why don't manufacturers offer a mixer tap and/or shower rail combo that could use the spare hole as the first fixing point and provide a riser rail that could bend or curve to one side of the bath. This could/would provide a more interesting and/or aesthetic feature to a bath/shower?
Perhaps they already do but if they don't, why is it always left to me to think of these things?
{Lobs an armchair through the window}
Arthur.