Reasons are obvious -- buses. If a good train runs, where the buses will go?
It looks funny to expect SWR to run a train from Coimbatore to Bangalore. Already Island and Kannur both are SWR trains. LTT CBE is a CR train. What is SR doing? They should propose a train from Coimbatore to interior karnataka in such a way that it benefits karnataka also.
Something like CBE 2130 KJM/ SMVB 0500/0515, ASK 0730, SMET 1030. Return SMET 1745, ASK 2045, SMVB/KJM 2315/2330, CBE...
more... 0715.
Thrice a week to Davanagere also can be explored.