I had meant to say "many" people---as in many people in my experience.
To me, it's not very surprising as in many countries your picture is customarily included in your curriculum vitae, and as Github is seen as a professional site akin to LinkedIn, people simply put up their pictures there as well.
This is anecdotal, but it's very rare for me to interact with someone on Github and have no idea as to their real name, gender, and face.
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I'll also add, there does seem to be cultural divide between us---as noted that you believe that people have to "feel a need" to add any information (photo/real name) that would show their gender when it isn't "necessary".
Whereas I feel that "real life" identification is the default, and pseudo-anonymity is a considered choice.
