[cleverwebble]

I'm wondering what % of forms that ask for gender actually use that field in any way

[xigoi]

Knowing the gender is necessary to produce grammatical sentences in many languages.

[rjh29]

That would be pronouns, not gender, right?

[nmz]

Which means gender should just be 3 choices, he, she, they. That's it. if a singular pronoun is used, its just changed to, "The person".

[csours]

Or in any meaningful way.

[perbu]

Unless you actually need to use gender for something useful I'm guessing it is a GDPR violation to ask for it.

[tialaramex]

I'm not sure why this was voted down?

This is Personal Information and so the data processor must have a specific reason why they need it, and must take appropriate steps to secure it. They can't just capture it "In case we need it later" nor can they just store it haphazardly because it's not valuable to them, or refuse to update it because that's difficult.

[nibbleshifter]

Violates the principle of data minimization, but I'm not sure if its on its own a violation that can result in an enforcement action.

[kace91]

I might be wrong but I don't think GDPR limits what information you can request, it's more about how the information is handled and the need for consent to collect it.