Alternating lefty & righty hitters is a logical strategy considering how teams use their bullpens now. In particular, most managers try to have their lefty relievers face lefty hitters as much as possible. If you string together a bunch of lefty hitters it means the other team can bring in a lefty to face a series of hitters. But if you alternate it makes it a lot harder for the other team to match up exactly how they want. So you either get a shot with a RH hitter against a lefty pitcher, or you force the other team to go through their bullpen faster.