Although BHU has the best faculty and management, many students tend to leave BHU after a few days. They feel isolated and homesick. Also, the teachers have a lot of political influence. The administration does not let you take a stand for yourself. A lot of inter students riots take place here.
Also, BHU has a sustaining hierarchy and preferential treatment that seeps down to the education part as well. Ex-students become professors without external exposure. So they bring much lesser value in terms of ethics, fair marking, and admission system.
I think these are some minor reasons why students keep leaving BHU after admission.