This distinction was first tentatively suggested by the grammarian Robert Baker in 1770, and it was eventually presented as a rule by many grammarians since then. However, modern linguistics has shown that idiomatic past and current usage consists of the word less with both countable nouns and uncountable nouns so that the traditional rule for the use of the word fewer stands, but not the traditional rule for the use of the word less.
I love that there’s a wikipedia page on this.
I hate that doing the wrong thing consistently automatically makes it the right thing.
Maybe you should read the article, especially the section on historical usage. Saying ‘less’ was never wrong, there was just a bunch of fancy academics that came along once and said it’s wrong, while everyone else just carried on as usual.
Annoys me that “less” is always correct, which makes “fewer” completely redundant, and yet it’s a short word that could be valuable in conversation if opened up and reused for something everyday that has a long name.
“Before I leave the house, I always check that I’ve got my keys, phone, and fure in my pockets.”
Use “less” for countable nouns and “fewer” for uncountable nouns as a little language prank.