TN AP and Telangana got those routes from long back. We have to history of Railways developments for these as in those days main and trunk routes are placed in those states and also those states have geographical advantages. I was also use to think like how u said now and use to be angry on our fate but no use some things will come on right time.. Slowly our state routes getting doubled and in future they get Electrified too. But still they will be not major routes as they face geographic constraint for speeds and also they won't connect metro cities with less kilometer. You might know even Karnatakas old rail routes handled by SCR and SR so they have better resources from long back compared to SWR which is new zone but it's improvising slowly now a days..i think after some years when lot of new...
more... lines open up then SWR also run good trains and it equally thinks about passenger trains facilities with freight profit..