[lapcat]

Oh, I might have misunderstood the question, because there are players who play a two-hander on both sides, but none who switch hands.

The answer is that most people are dominant on one side, right-handed or left-handed, and their non-dominant side is much weaker, so a right-hander hitting a left hand "forehand" would be much worse. That's just how our brains work. :-)

The thing about baseball is, all hitting strokes are two-handed, so it's more analogous to the two-hander from both sides than the one-hander. Also, baseball hitters don't have to run to the ball. :-)

I would guess that the second hand in baseball helps a lot with stability and accuracy, because a baseball is so much harder than a tennis ball, and the barrel of the bat is so much smaller than the string surface of a tennis racquet.