Earlier quoted context omitted.
Especially if you are a germ-a-phoebe like myself. My friend accidentally sat in a seat soaked in urine by the previous passenger, and had to go back home to change clothes of course. I decided ... nope. And then there is the occasional smoker, so if you have asthma ...
Going by the descriptions here, riding the bus in the US is worse than riding one in India. In Germany, smoking on a bus is unthinkable, and the bus drivers (and other passengers) will throw you out pretty much immediately if you lit a cigarette. I've also never heard of people peeing in the bus, let alone encountered that, even though I regularly use public transit at all times of day and night.
You seem to be under the impression that the US is an advanced country full of civilized people like Germany, Norway, Japan, etc. You've obviously never been here.