Why the generator does not back emf?

A generator does produce back electromotive force (back EMF) as a result of electromagnetic induction. This back EMF opposes the applied voltage and limits the current flowing into the generator. However, if you are referring to a specific scenario or condition under which a generator might not exhibit back EMF, such as when it is operating at no load or when it is stalled, then it may not generate significant back EMF. In those cases, the lack of mechanical motion or load leads to minimal electrical generation.