The most accurate answer is that children were often hired to work in factories during the Industrial Revolution because children could fit into tight spaces between machines and could be paid smaller wages, so factory owners hired them.
Factory owners sought to minimize labor costs, and children were cheaper to employ. They also had abilities, such as being small enough to crawl into tight spaces for tasks that adults could not easily perform. This economic incentive was a significant factor in the widespread use of child labor during this period. Additionally, the lack of regulations around labor and the prevalence of poverty made child labor a common practice among families in need.