The Konkan route is a high speed route. It has moderate to low gradients and is mostly a pretty straight route with no sharp curves. The terrain is challenging there, but as it runs along the relatively plain coastal regions, it was possible to construct a high speed route albeit with considerable difficulty.
This route on the other hand, passes through particularly hilly tracts where a straighter, faster alignment may not really be feasible. That said, operating speeds can definitely be improved, but it is unlikely that IR would bother to keep up the rigorous maintenance and operational procedures required to do so. And given the lack of alternative means of transport, trains, even if they...
more... are slow and few in number, would always be in good demand there.