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.
Top 13 Quotes by Al Kaline
Carl Yastrzemski was the best all-around player. He could run, throw and hit. He had the ability to play a number of different positions. He signed as a shortstop. He could play the outfield, of course, and third base and first, too. He was a tremendous athlete. Mickey Mantle was unbelievable, too.