Self-diagnosis
Self-diagnosis (or self-dx) is generally accepted in the Autistic community because it is often both hard and expensive to get a formal diagnosis. In many cases, the individual may think it isn't even worth pursuing. Many people self-dx after both thoroughly researching online Autistic communities and a lot of self-reflection, something Autistics can tend to do a lot of.
Barriers to receiving a formal diagnosis include: sexism against women being recognised as Autistic, racism, poverty, lack of access to healthcare, lack of access to queer-accepting healthcare, and many doctors refusing to diagnose adults who were not diagnosed in childhood.
Some people may also avoid receiving a formal diagnosis due to the stigma received from having an autism diagnosis on their medical record. In particular, autism diagnoses have been used to deny child custody, access to medical care, entrance to some countries, and general autonomy.