You could flippantly say that there's no system that has enough fields for all the options.
But really there is no demand for the data.
The system I saw data from recently was categorised into male, female, other, prefer not to say and no answer.
The numbers for anything other than male or female were miniscule, more opted out completely, and I honestly don't see it ever being used as it's just more lines on complicated reports with empty boxes or with "4" in it.
Despite the clamour for the life saving nature of validating identities there's barely no-one wanting their identity validating.
Men already pick female if it makes them feel better and disappear into an aggregate soup.
(Yes I know how you feel about that but that's not what my post is about.)
Breaking "other" down takes me back to my first point, before you even set up the 799 gender categories in a system you need a committee of 400 to squabble over the 799 categories for 6 months with safe spaces available.
Nobody in the systems team can be bothered with all that unless they are a complete evangelical from Canada or California.
And no-one wants headcount data reports broken down into male and female plus 799 mostly empty categories. The reports would add too much to the global power usage stats for a start.
It's reaching it's pointless end.