Let's be honest. Safety and liability issue is a convenient excuse and in reality, a small part of the reason.
The developmental aspect is the real reason. When you're talking about the 7/8/9 grades, the point of Little League is to get the attention of scouts for professional organizations and colleges. When you introduce millions in signing bonuses to an 18 year old or athletic scholarships, you're begging for adults to poison the well. Little League has a history of cheaters and the organization, at best, is frequently overwhelmed in dealing with them.
The developmental aspect is the real reason. When you're talking about the 7/8/9 grades, the point of Little League is to get the attention of scouts for professional organizations and colleges. When you introduce millions in signing bonuses to an 18 year old or athletic scholarships, you're begging for adults to poison the well. Little League has a history of cheaters and the organization, at best, is frequently overwhelmed in dealing with them.