You don't need the Internet for ambiguity to occur, you only need to go international. It may be because you travel, or work with foreigners, or handle mail/packages to/from abroad. Or use any kind of software, because unless you live in the US, almost all software you use is made by foreigners in a foreign country.
In a globalized economy, local date formats are just one of those annoyances that serve no benefit, cause everyone unnecessary hassle, occasionally causes expensive errors, and that should have long ago been replaced with an international standard.
On government forms (and other paper forms), I use 3/11/2021. It's unambiguous; nobody would expect it to mean anything other than "3rd of November of 2021". The ambiguity only happens once you add the Internet to the mix, and even then, only in English-language websites (I wouldn't expect anything other than DD/MM/YYYY on Portuguese-language websites, and the same probably applies to most other languages).