AskBeehaw

Uhh, most things?

Trying to think where it might not be unnecessary, and can only think of three.

1. Seeking out a particular gender for mutual support, therapy or medical care if one has had difficult experiences surrounding gender & sex. I don't know that this is fully healthy, but to date barely any humans have ever had access to the sort of idealised therapeutic environment where working through that safely is viable, so everyone is trying to get through as best they can.

2. Within some sports the differences conferred by sex are dramatic enough that it does not seem unreasonable to have competitive divisions on that basis, though I feel a more finely-grained approach would be more appropriate for a great many reasons not limited to sex & gender. Many sporting bodies do permit girls & women to compete against boys & men, but female athletes seek out their own divisions in order to succeed.

3. Sometimes useful as a short-hand in conversation. Hard to argue that it is necessary however, and it may be that if society were to be in recovery for long enough, that this utility would ebb away.