One of the reasons may be other Superfast trains running ahead. Just consider Mumbai-Jaipur Superfast and Avantika both starting from Mumbai Central and taking only 3 hr 40 min and 3 hr 48 min ( 10 min reduced for Mumbai Central to Bandra time) respectively whereas this shatabdi spl with shatabdi fare of Rs. 465/- takes 4 hr 15 min. Total collapse of the train success. Even if the time is advanced to 6.45pm or even later @ 9.30 pm, the train will run almost empty as the travel time and fare both go against the passengers flavour.
The ideal way to run the train is simple SF train without compulsory catering with II class and CC coaches and...
more... the dep timing between 7 - 8.30 pm. and travel time at the most 3 hr 30 min.
The timings of this train have now been scheduled to run behind Mumbai-Jaipur Superfast and Avantika Express. A better time would have been to depart from Bandra by 6:45 pm so that it could run in front of these 2 trains and reach Surat by 10-10:15 pm.