Ahh, yes, double walled! They knew something about insulation back then? Forgotten since?
Yes, there is likely a reason and here is a related item, which may interest some. Early vintage cars were originally drained of coolant, if left outside overnight during the winter. It was not long before antifreeze was adopted by most - methanol based ones which evaporated quite quickly, mostly. However as the 1920s passed by, and into the 1930s, the winters becames so mild that it was thought that antifreeze requirement would soon be a thing of the past, at least in southern Britain. How wrong they were!
But maybe this period saw the change from better insulated to lesser insulated and it stuck? Bees survived adequately with only top insulation (quilts), often ofvlayers of old carpet, newspapers, etc.
Just guessing, but thinking back over the last 40 years, the following might be 'thought for food'. The last annual skating races held at Baston Fen in Lincs took place around 40 years ago - the ice has not been thick enough since and not much ice skating has taken place at all, until a couple or three years ago. Last winter, antifreeze in cars was hardly needed at all in large swathes of the UK. Only a couple of decent frosts and no real prolonged drops to sub-zero. OK, the previous couple had several periods of freezing temps (triggering extra heating payments for the elderly, infirm and poorer sections of the community), but they were odd-ball seasons if compared with the last twenty years.
The last time our town was cut off by snow was thirty years ago, and occurred quite regularly before that (local quarry machines used to be sent out to clear the roads in those days). Many would not remember 1963 (I do) and very few 1947 (before me). Apparently high colony losses occurred in 1963 - possibly the cold actually killed the bees, or perhaps the duration caught out a lot of keepers, who knows? There would still have been a lot of double skinned hives in use back then. Just a bit of food for thought.... Maybe these cycles are connected to changes in attitude towards insulation, and single or double-walled hives, just maybe....