I have the following reasons :-
.
1) HWH's Platforms are all land connected so no issues of overhead bridge for Senior Citizens to board this train like in KOAA.
2) The distance between Howrah & Dankuni is much shorter than that between Kolkata Chitpur and Dankuni so reduction of travel time for this train.
3)...
more... Howrah Station is much more easy to access than KOAA, SRC or SHM. The Sealdah Station can be the 2nd Option. Some other train from HWH can be shifted to KOAA for swapping with Durgiana Exp terminal change.