Yeah I know, but it also has a different use case. As far as I know RFC3339 is mostly used for programming while ISO8601 is the standard for international communication and I wish people would use it more. I have processed American invoices in the wrong month because of their date structure. I have no reason to it, but I always write my date ISO 8601 (YYYY-MM-DD)

The omitting of timezones doesn't matter to a vast majority of the world, since most countries only have one time zone so I don't see a reason why that is relevant in most use cases.

ISO is a general standard, it's in the name and the RFC is created for the internet, that is also in the name/description of the RF.

Using 2025-164 can be handy, I actually use the day of the year to check what invoices from previous year are open since those are the invoices that are due 164 days or more.