An interesting subject that I don't know a lot about except from my own observations.
The wooden bat is not as uniformly constructed as the metal bat. The wood has a differenct density than the hollow metal bat.
The wood absorbs more of the energy of the pitch than the metal does, requiring more power from the hitter to drive the ball the same distance.
The wooden bat has a smaller "sweet spot" requiring a more precise swing to the ball. The wooden bat is less forgiving, in other words.
Swinging the wood develops more muscle in the body.
I would equate it to using resistance weight training, or weighted balls, maybe.
So, when you practice with the wood, and then go back to the metal, you will realize a significant increase in your hitting.
And, a lot of young players like to swing the wood, just to see what it will be like someday.......