Change in time Slot is the Main Key Feature here.
Because it shares Slot with BDTS AII/UDZ Express and Bandra Patna Express and for making one train Daily, they wont Change time slots of 2 other trains. Naturally it will be given another time Slot, and on this Congested Route, no other Slot is available as of now. And Moreover WR never gives Priority to Any train other than its own Zone trains, Just one Exception is Swaraj Express, that too because earlier it was WR train only.