For reasons, the reader must refer to the advantages of wooden bats described in the coming lines. As one goes from little leagues to major ones, the use of wooden bats becomes a tradition keeping in view their material, weight, safety, and affordability as compared to aluminum (metal) bats.
Wooden bats: Wooden bats are heavier than metal bats because they are solid, and that is why they require more effort to sway than aluminum bats. They also have a smaller sweet spot due to which the hit remains within range, that is, the hitting zone is small. In other words, the weight of wooden bats is concentrated far from hands, or in other words, the center of gravity lies in the barrel. Thus the “swing weight” (Nathan 1) is higher which keeps the ball within range.
Metal Bats: Metal bats are hollow from within. A metal bat is lighter because of a larger sweet spot, and the weight is concentrated very close to the hands, which will have the hit swing much higher as the swing weight is lower.
Wooden bats: Wooden bats are safer than metal bats because the exit speed of the ball is much slower in the case of wooden bats. Thus, the ball comes off with a slow speed which is good as it reduces the danger of injury if the ball hits another player or pitcher. This is why MLB endorses the use of wooden bats considering the hit power of the professional players.
Metal bats: Metal bats, as they are lighter, can easily get tossed away to injure another player. Also, the larger sweet spot in case of metal bats causes larger exit speed of the ball, that is, the ball will jump off faster which could injure anybody within the hit zone very seriously.