It's an interesting question.
The National size frame was around long before the hive was designed. There's actually a lot of advantage in standardising the frame. Many have made their own boxes and expected them to last 10, 20 or more years. In that time they will be fitted with several sets of frames and home made frames are seen much less often.
The Langstroth seems to have become established across the US without other formats getting a look in. That might be connected with the way the US always had more migratory beekeeping and bee farmers on a larger scale than ever appeared in Europe. The economics of standardisation and mass production were felt for hives in the US before they were over here. The same argument probably applies to Australia and New Zealand where the average size of the beekeeping enterprise was larger than here.
If you look through the late 19th, early 20th century British magazines there were many varieties of hives being made and advertised. Some recollections written a few years back said the most popular hives between the wars around here were WBC, but firms in the area were making varieties of "Simplex", "Cottager" and their own designs. If anybody did want a larger frame size, there was always the Commercial format available from the 1920s. Practically most of the others took the long lug National frame as far as I can find details. There was an effort by the Ministry of Agriculture before the second world war to promote standardisation. That's essentially where the National hive came from, the first ones arriving her in the late 30s. They were heavily encouraged officially during a massive expansion of beekeeping during the war.
Beekeeping remained popular after the war until sugar rationing ended in the 1950s. By then there were lots of national size boxes available, so for a shrinking beekeeper population who could use the existing boxes there was no point in changing formats. It's easier using the type everyone around is using than being the only one with a novel format. Don't be misled by the size argument, the written National standard has always allowed for more than one box for the brood. Whether that's deep plus shallow or two deeps the multi box format is adaptable.
The question leads to why did Langstroth sizes become popular in Europe? My guess is that, while many areas had their local formats, there was no organised standardisation effort as for the National in the UK. The result by the 1950s/60s was that Langstroth became a popular cross border format that would allow parts to be sourced from various suppliers. The local formats are still going in wood, but the extra investment in moulds that making poly hives needs tends to mean that Langstroth has dominated that market as the first format to tool up for.
