There is a lot more surface area on a racket, compared to the bat. Also, even fast playing hard or grass courts slow the ball as soon as it makes contact with the court. In my opinion, it is easier to read a serve and get a clue on where it is going than it is to read a pitch. Placement of the toss, location and angle of the body, and rotational delivery all give clues to the returner as to where the serve might be placed. Also, a lot of time returning a very quick serve doesn't require a swing - just placing the racket in front of the ball and "chipping" it back into play. A batter has to connect on a full swing, and even a bunt is tougher to execute than a chip return. I haven't played college+ level baseball, but have returned countless 130 mph+ serves. It's not easy.