Selection bias. Notice how most present day groups are in hot and relatively stable climates, areas where one can hunt/gather all year. Look to past groups in the north where seasonal changes meant the window for any particular food source was always limited. When there is only a short window, it is maximum effort from everyone.

The same is true for agriculture. Even today, with all of our mechanical wizardry, farmers on the plains still pull their kids out of school to help during harvest.

Your previous comment was far too absolute in its wording and was thus incorrect, as evidenced by GPs counterexample. "Four guys going into the woods and spearing an [animal]" is definitely not "a myth".

Note that many early humans lived in "hot and relatively stable climates".