Because every country had it’s own measurements. Some places had pounds that weighed different amounts from other places. Nobody would agree to use “THEIR!” system — only a brand new system could bring everyone together.
My latest information was from 2022, but: In 1975 the price for a dozen eggs was 88 cents; when adjusted for inflation, that was the equivalent of $4.79 in 2022 dollars and was the highest it had been in the 50 years leading up to 2022.
I wanted to name my dog “Quaaludes” so I could wander the streets at night calling for her name whenever she ran away, but nobody would go for it.