Here's why:
* Poverty: Districts like 11 and 12 are the poorest, with families struggling to survive on meager rations and dangerous work.
* Lack of resources: These districts lack the resources to provide for their children's basic needs, let alone education or training for other professions.
* The allure of the Games: Winning the Hunger Games brings immense wealth and privilege, making it an irresistible hope for many impoverished families.
* "Voluntary" participation: While not true volunteering, the pressure on children from poor families to participate in the Games is immense. They feel obligated to sacrifice themselves for the chance of a better life for their families.
Examples in the books:
* Rue: From District 11, she is shown to be very poor and rely on foraging to help feed her family.
* Katniss: From District 12, she hunts and forages to provide for her family, and her participation in the Games is seen as a way to save them from starvation.
The Hunger Games highlight the brutal realities of poverty and desperation, and how those in power exploit the vulnerable for their own gain.