What is the reason for the androcentric nature of the Tripitaka?

I am focussing my answer only within the Theravada context which preserved the teachings in Pali. Theravadins believe that their teaching is most authentic from a historical point of view. We need to understand that the Tripitaka that we know of was not a written work from the Buddha's time. Religious knowledge was to be practised and handed down from teachers to chosen disciples. Hence no religious teaching was recorded. This applied also to the teaching of the Buddha. The Tripitaka was first recorded in Sri Lanka not before 450 B.E. (about 90 B.C.)

What was recorded was according to the understanding of the monk recorders. What they chose to record was subjective, hence it is understandable why the Tripitaka is androcentric. The Tripitaka was recorded by men who were ridden with Indian social values. They were men who by the vinaya, were expected to lead lives of purity. The most immediate obstacle to their chastity was the opposite gender. Many teachings as preserved by these men therefore projected women (embodiment of their obstacles) as evil, unclean, etc. This is a necessary barrier to fence themselves off from failing into the pit of the unchaste. While reading the Tripitaka one must remind oneself of this limitation in order to sift the essence from its social contextual limitations.

Looking at the teaching from the Paramattha level, one sees clearly that Buddhism is free from gender bias, Buddhism is the first religion in the world to recognise the equal spiritual potentiality of men and women. This provides a special place for Buddhism which started in India to lift up to the world spiritual level without boundary in race, caste, or gender.