Because this route collect a lot of passengers in this area & this area is always suffering for good train. This route can do two important role.
1. Fast connectivity between Gorakhpur & Allahabad (355Km. Other train takes almost 9 to10hr. and collecting a big no. of Passengers.)
2. Allahabad-Kanpur Route have so much fast trains like Rajdhani, Yuva, Skr, SF. Some train have Distance restrictions & Some no stoppage. This Janshatabdi helps also for up-downers between Allahabad & Kanpur with fast connectivity.