While i do agree with you , I think daily trains should at least start from TVC and maybe the weekly biweekly could be shifted to KCVL. But in both these two trains (KCVL-SBC and Sabari Exp) i guess their timings i.e arrival and departure from TVC is at a peak time when the station witnesses very heavy rush with lot of other departures/arrivals so maybe that could be the reason!