My take is that these guns were of their time.Post war UK shooting was generally low volume ,social outings .The era of commercial shooting had not arrived and the people that bought these guns would not fire many cartridges in a season,even in the 70`s you rarely saw a slab of cartridges sold!!!
...so light weight was a trade off for portability as more walking than shooting was the order of the day.
Those few involved in big shoots bought something else !
Just my take on it all.