The old wingloading formula will likely remain the favorite - it is easy to do and like inches and pounds - is pretty well accepted by the public -her in the hew ess hay
A "better" method may NOT be better to those who simply want a quick easy approach.
If metrics were truly better - for everone -why isn't it the prevailing approach in all countries
because many people simply would rather go with tradition -it's easy and for them "good enough".
Crikey -be glad things are not measured in furlongs per fortnight.