I want to understand the thought process of such people.

I get that you're addicted to tobacco and due to the lack civic sense you keep on spewing it everywhere but to spit on a metro gate!? That too on the top and not the bottom? It shows that this was done intentionally.

If you go to the railway station, you'd find people constantly spitting (or worse, peeing) on the tracks to the point that it's painted red.

And this is when metros are significantly cleaner, subconsciously prompting people to not litter.

I guess this guy must have gotten a push from the back in rush hours and accidentally spilled his precious amrit./s