Yes! Actually IR should. But this is how it works. The catering services are offered through tenders to private parties. Railways does offer tenders for almost all long distance trains. But then it's at the mercy of the third-party caterers to asses whether the route is profitable for them or not. There are quite a few long distance trains which do not have pantry. The reasons could be weekly service, kind of passengers who do not spend much on food, and over all non-profitability.
One alternate solution would be for the railways to provide their own catering (non-third part) and serve the same to the passengers. They anyways do that by taking orders from passengers and supplying the food from some...
more... important intermediate station, however an in-house railway run PC would be an added advantage.!