The study of garbage has given us much insight into civilizations of yesteryear. It has been instrumental in solving crimes. It has even resulted in the fall of an American president.
Humans are by their very nature careless with trash.
It is not a trait of the 20th century. Garbologists have discovered that people let trash fall where it may. Four basic means of dealing with trash have been used over and over in history. The Mayan Indians of Central America had dumps, which exploded occasionally and burned. They also recycled.