They are not focusing on tier 1 city routes in North . Plus north already had Shatabdi connections .
IR is completely ignoring Ndls and probable pairs like LKO , JU , UJJN, Kota , ASR , JP, UDZ etc routes .
Secondly...
more... North (Delhi Haryana Punjab UK and West UP) is connected with 16 coach VBs while South India has mostly 8 coach VBs
Thirdly Highway / E way infrastructure snatches many probable passengers in North as compared south , where VBs are aggressively scheduled and kept as the fastest mode between pairs apart from Air mode ..