[Aquattro]

Mason, are they necessary? No. Are they benificial? Yes. Before I started using a wave maker, I noticed the sps' growth pattern was dependant on the direction of flow most often hitting them. Alternating the flow gives a more symetric growth pattern, IMO. It also changes the current slightly each time it passes a coral, which is more likely to wash away waste materials.
If you be creative with a couple of cheap timers, you can simulate a wave maker without the high cost.
A lot of the "toys" in the hobby aren't necessary, but many of them do provide varying degrees of benefit. Whether it is worth $200 to change current is a personal choice.