Assumptions is also one of the reasons for a long-lasting trend towards reducing the information on passports where it risks misleading. E.g. my first passport had hair colour and eye colour, and a colour photo. The hair colour and eye colour was removed because it was increasingly just confusing and unreliable, and the photo is now black and white. I'd expect gender/sex to eventually be emphasised or removed too, for the same reason - it's not particularly helpful as a means of ID'ing you unless you do a medical examination.