Advertisements. For some years, Mackeson has been a 'ghost brand' in the UK – still produced and sold but without advertising or promotion.
In similar fashion, berliner weisse and gose sour beers have taken to the use of lactose as well. Brewers like adding fruit to these styles to balance out the tartness and give their customers variety. Lactose fits naturally to get the added sweetness that many beer drinkers are seeking.