What does American date formatting have to do with anything / anyone outside of America?
If you see a date somewhere, you can't ever be 100% sure that it's dd/mm/yyyy, as an American may have written it. On the other hand, yyyy-mm-dd is unambiguous.
DMY is the perfect progression.
That's not the case when written with a time next to it, because in that case it's inconsistent and "backwards" compared to the time. The date goes from "smallest" unit (day) to largest unit (year), yet time is written the opposite way, with the largest unit (hour) to the smallest unit (seconds or milliseconds). If you instead do yyyy-mm-dd hh:mm:ss, the entire thing is in a consistent order.