Q. Why does Imaam Abu Hanefa not allow woman to perform salaat with jamat as Imaam?
A. Imaam Abu Haneefa does allow for woman to perform their salaah in jamat (group form). He does allow woman to lead in salaah as well. However, woman as Imaam is with karahat (viewed as a reprehensible action). It is best to be avoided when possible.
Allah Certainly Knows Best.