I even found this article about how "and" doesn't actually mean decimal point: https://www.grammarphobia.com/blog/2012/02/decimal-point.htm...

I think it dates from the time when the only decimals the average person would use were in currency.

Your link is the only one I could find on the first page of google that states "and" means decimal point. Every other source I could find says "100.17" is either "one hundred point one seven" or "one hundred point seventeen".

I think people are forgetting, before the days of numeric calculation by machines, there were rooms full of people tasked with keeping track of these things.

back when we wrote checks, you didn't write the word "and" till you got to the cents (US) on a line that was preprinted "dollars": one hundred fifty three cents dollars" vs "one hundred fifty and three cents dollars".

It's history, it's interesting, it's not meant to throw you into a panic or fits of anger. And I very much doubt that you speak for all of English speaking countries, and through history as well, but must admit you might and I'm lucky to encounter an historian of numerical orthography.

(Update: unless the units were expressed after the following number, like 5 dollars and 13 cents, which still wouldn’t express a decimal point.)

it doesn't express a decimal point if you think of cents as a completely different unit of currency from dollars, but if you think of cents as 1/100ths it actually does indicate the decimal point. "5 dollars and 13 100ths" which is what cents means, and which is sometimes used when not referring to money, for example items that are measured in centiles such as interest rates. I think our forebears were more likely to throw words like centile around, and thats how they came up with the word cents.

My cousin is Italian and he always says "for cent" to me and I scratched my head till I realized, per is translated to for from Italian, and they say "25 per cento" so he's just translating it to English as it makes sense to him, not realizing we also have the word per.

For more interesting currency matters, go back to https://en.wikipedia.org/wiki/£sd#Writing_conventions_and_pr..., where you had three items, and “£2/4/6” would typically be pronounced “two pound, four and six” (or sometimes “two pounds, four shillings and sixpence”). This shows more clearly that what it’s a perfectly normal “and” like any other in English. (Also that conventions can certainly allow elision in understood contexts. I’ve never heard of “one dollars and twenty-three” for “$1.23”, but it would be consistent with the sorts of shortenings that sometimes happen.)

and fwiw, I don't think it's a regional difference, I think it's a difference between certain traditions within the banking and accountancy areas, vs outside.