Some of it is cultural. (I can't speak to their engineering practices or limitations, anyway.) Toilets aren't a given in India. They're generally available in cities. But, for example, on some locomotives, the toilet is a literal shithole cut in the floor, for you to you void directly on the tracks.
source: was tourist
relevant article picked at random: https://www.washingtonpost.com/world/asia_pacific/india-is-b...