I am going to do a rare thing - for once I will support the BWMA in order to put your questions into perspective.
The BWMA was founded towards the end of Queen Victoria's reign to oppose the infiltration of British weights and measures by American weighs and measures bearing the same name but having a different value.
You do not seem to understand that in the United Kingdom there is only one pint - the Imperial Pint (approx 568 ml). The use of any other pint was declared illegal during the reign of George IV. Ther long list of pints in the reference that you keep on producing is the reason why the UK settled on using one pint only.
I have also checked the one reference that you seem to keep on refering to - while it is interesting is is very US biased and yet it omits a whole raft of US measures, not least of which is the Vara, which is the official unit of length in Texas when measuring land.
I've come to my senses. My understanding is that BWMA was set up to oppose the metric system. However, Martin's alternative explanations of BWMA's founding could be true. Unfortunately, a lot of the historical records were destroyed in the 1921 fire.
Saying that the Vara is an 'American' unit is a bit disingenuous.
It's used only in Texas, and is in fact a traditional Spanish unit. It is the official measure of land area because land records had been measured in Spanish units well before Texas became American.
Even here in Florida, also once a Spanish possesion, all land is measured in acres.
The predominant system of measure everwhere in the US, including among the Spanish-speaking community, is English units.