Not to mention, sometimes the reasons for these traditions was rooted in a long, outdated logic or is simply no longer applicable.
Not sure of the history behind pitcher/catcher hand signals, but if it's anything like the history behind the signs used by the fist base coach and third base coach, maybe it can go for the most part. Base coach signalling was only started to accommodate former Red/National/White Sox CF William "Dummy" Hoy, who was deaf.
Now if there are any deaf/hard-of-hearing pitchers out there - and there might be (the Angels recently had hard-of-hearing southpaw Kevin Grendell in their minor league system for example), hand signalling will be a necessity for them. But so far, there have only been a handful of deaf players in MLB...