It indeed a popular question, and as for why, I can think up a few reasons. I'm not a psychologist, and I won't pretend to have any definitive answers, but these are my own personal opinions and observations:

- Personal sense of identity
When I first realized I was a zoo, and accepted that fact, this kind of question kept bouncing around in my mind. For some unknown reason, I felt compelled to try to identify how I could describe myself. Basically this was just a another way of coming to terms with myself and accepting who I was.

- Public sense of identity
Whether we like it or not, labels exist in society, and people will always be classified and grouped with these labels. Some people don't feel truly comfortable unless there is a specific label to define which group they belong to exactly.

- General expression to others
Some people may just be genuinely interested in how you would describe yourself to others, either the general public, or close friends. For example, if you're zoo exclusive, what answer do you give to the question of your sexual orientation? If you don't want to lie, then it's natural to seek the closest and next most specific label possible. I have personally wondered how I would describe my orientation to others if I was in a position where I had to. I have tried to decide how I would respond in such a hypothetical scenario.

- Reassurance, insecurity
People want to know if others agree that the chosen label is appropriate, a simple second opinion to verify if they chosen the correct label or not. This further helps people to know they've found their true place within a group, and can put one's mind at ease. Just think of the countless people who have come here for answers, searching for reassurance that they weren't alone in their desires.

I agree that labels are unnecessary, and in a more perfect world, they wouldn't be needed. But it's for these mental reasons that it helps to identify who you are. For whatever reason, if your mind seeks the answer to such a question, then it's important to find out, otherwise it will always be a nagging thought in the back of your mind. Once someone finally realizes who they are and how to describe themselves, they will feel some sense of relief. I know it seemed that way for me. Once I felt able to describe who I was, I had this sense of clarity and contentment. From this, I assume that the majority of people out there seek similar answers, hence why this question is so popular.

I don't know why, I just felt compelled to say all of this. But that's enough rambling for now...

Hmm, nice analyzation work there. 10/10 for your time and effort.

I agree in most respects. However, it is possible to completely avoid labels whatsoever. Just takes concentration on not caring.