To directly answer your question, No you have no real need to put it on. It only comes in hand if the filter is almost entirely submerged. (meaning you drive through a 2 foot deep puddle)

I had had my AEM CAI for at least a year before they even came out with that bypass valve, and I have had 0 problems. Also, there was actually a recall on the orginal bypass valves, they had a problem with one of the parts (i cant remember now) coming off and getting sucked into the throttle body causin serious problems.

So in short... No you dont need the Bypass Valve, unless you like to take your car through LAKES of water.