On an average 320 buses run from North to Delhi via Chandigarh Ambala. These buses are almost 60-80% occupied if not 100%. The fare is also around Rs. 170-200 per trip.
Now you see 2 shatabdis and 1 Janshatabdi run between CDG and NDLS.
We still have scope for 1 DD here. Those who cant get seat in Shatabdis have to go via buses.
There...
more... are white elephants like INDB-BPL DD and there are routes needing for trains like CDG NDLS. Also per capita income in MP is much less than Chandigarh so it is obvious that people are not using BPL INDB DD.