Because everyone else at Tumblr more or less young, male, single, caucasian, straight, European ancestry. The Office manager was female, one of the HR reps was African American, head of security had kids, PHP developers were always blowing through so occasionally someone diverse would slip in there, but in large LGBTQ was the only category where there was diversity and they hired a lot from that category. If you were LGBTQ and had a cat it was more or less impossible to not be hired. All this would come up occasionally in the Friday company meetings and David would always promise to do better but the demographics never shifted much.

One of the Unix admins was allergic to dogs if that counts towards diversity.