Railway assumes stations in West Bengal have good connectivity by default. On top of that ER takes BWN as suburban head for granted. Only premium chair car train i.e. NJP Shatabdi which halts at BWN fetches ~55 assignations in each direction.
Similar examples exists. PNBE HWH VB skipped DGR in initial tentative TT. Later added after political intervention. Now look at the patronage it provides. TATA-PNBE VB also avoids PRR inspite of slot availability and better path. Infact all new trains introduced recently avoids PRR after CNI.