All 4 cities (Sonipat, Panipat, Karnal and Kurukshetra) have high demand to connect Gurgaon, Jaipur, Ajmer, Ahmedabad, Bandra via this route. So, railways can't decide which one to give and which one to leave.
But I tell you Panipat gives most number of revenue generating pax followed by Karnal then Kurukshetra and Sonipat.