One reason outfielders don't have stronger arms might be they don't practice as much as we did. Most teams today don't take outfield practice. Another reason is baseball has to compete with other sports now - basketball football soccer - for the better athletes that might have more skills and stronger arms.
I was always on the go and thought I was too busy to develop something like this. I thought at the time that diabetes went along with bad habits but I was the last one in my family to eat junk food.