Why its necesary to forward biasing the base emmitor

Because emitter is heavily doped as comapre to collector and area of emitter is less than collector. The EBJ emitter junstion has to be fwd biased to drive more electronic current and the reverse biased CBJ helps to collect the electron at the collector terminal to flow it outside, by applying more and more reverse bias to CBJ will cause more electrons to collect at collector and increase in flow of collector current. If reverse is happened i.e. FWD bias CBJ and reverse Bias EBJ then very little amunt of current flow at emitter because of difference in areas.