Other than the desire to label everything and everybody, it's also attempting to merge biological identification with orientation into one label.
Biologically, there are "male", "female", "both" and "neither". The occurrences of the latter two are very low in comparison but they do exist. To further complicate this, questions such as "is a female who is 'born' with no ovaries truly a biological female?". Best not to answer this one unless you want a very long discussion, but it's an example of how things are complicated.
Beyond the straight biology, for many thousands of years humans themselves have blurred the lines, starting with eunuchs and cross dressing and moving on to trans-sexuals in various applications and stages (surgical, hormonal, etc).
This is before the complication of sexual preference comes into play where the basics are accepted as male-female, male-male and female-female however these basics only take into account the two primary biological sexes. Expanding just the biological side and sticking to pairings there are ten distinct combinations. Add in those who are interested in more than just one partner type and it becomes quite a mess. Next include the non-naturally occurring "genders" and it's one hell of a matrix. Lastly, don't forget those who have no sexual desires at all and are happy that way therefore they shouldn't be identified as one of the others.
Even attempting to refactor the single label into a few becomes an exercise in pointlessness as no single label will fit all unless there are n! combinations. So in essence, it's a multiple choice list and not a single selector, after all your work colleague could be a heterosexual man during the week and a cross-dresser that is only interested in other cross-dressers at the weekend...
50+ doesn't seem too insane a number considering...