Need is a relative term. I will warn you that you are not a "real man" without a 9mm 75B. They grant their users "real ultimate power" and greater CZex appeal. Without a 75B, life has no meaning...hahahaha! Sorry, couldn't resist.
Kidding aside, they are the "standard model." (Actually, a pre-B is the standard, but you would have to search for one of those a bit.) All of the other pistols are departures from that one. I like having one for that reason alone. I am a bit of an "accumulator" though. I would like to have a Witness and Jericho to go with my three CZ 9mms. At this point in my life, I could shoot my CZs and a maybe a few clones, and I would be totally satisfied. I really love them that much.
I may have a change of heart some day. I shoot with my dad a lot, so I do have the occaisional change of pace. I am tempted to get a S&W Model 64, since I may be moving out of my home state and no longer able to shoot pop's. I would really rather have another CZ deep down, but I know I don't "need" one.