Dunno J*Ace
Loads of influencers I guess mate..... History, economics, market share, merchants and dists, shelf life, UK spreads choice and experience....... etc etc.....
If the good and hardworking spreads of the UK demanded a change and went in to the suppliers and stated "get some Knauf MP Finish in and we will use it!!" - I am sure the outlets will and things might change.....