Bus and shuttle riders tend to eat as they travel, and food containers, once emptied, invariably go out the window. This was the case in every country to which I traveled except Belize, where litter-prevention campaigns have been in place for a few years. Everywhere else, trash goes right out the window. No one acts furtive or guilty when they litter it is an accepted action. People sitting on interior rows can pass trash to those seated near windows to be tossed out.
Buses bear signs admonishing passengers to keep our bus clean throw trash out the window.
My attempts to tell a couple of children that littering is bad for the environment, country, etc. were met with stares and giggles. They continued to throw trash even while I was talking to them. All but the largest and most remote lakes are polluted to such an extent that fish may not be safe to eat, and swimming is sometimes discouraged. Water from sinks and showers usually is piped directly into the lake without filtration. Villages near medium-sized rivers pipe their waste directly into the stream, for downstream communities to deal with.