The anime girl profile picture for some, becomes a manifestation of the Jungian anima. Because sex does not exist in this digital world where only our minds can travel within, a male in particular is prone to manifesting particular aesthetics. Greek statues, anime girls, those guys wearing sunglasses that all look the same, its all contained within a psychological typology wich breaks down further into subsets. In the case of the anime girl, you have really two or three camps. "I enjoy moe" and "I choose to engage in this behavior as a conscious subversion of the concept of gender on the internet. I am sometimes misrepresenting myself as female but not in an attempt to deceive for deceptions sake(catfishing for example). I am engaged in an esoteric display, and perhaps unaware of why. But to make these things explicit would dissolve my mystique."
Its very common on political anime twitter where everyone is either trans or a schizoid with a god complex.