Wow, just stumbled upon this post, Pretty funny comment about the antisocial geek, which is kind of true, if you want a keyboardist that can program different synth sounds.
As a keyboardist, I do have some ideas as to why finding a keyboardist is hard. I don't hang out in forums with other instrumentalists, so I apologize in advance for any assumptions, insults and short sighted comments. I don't play other instruments, so it is likely that my viewpoint is limited. Please correct me where needed.
Problem #1 - The teaching community is geared towards classical sight reading. Eight years of classical training in my youth gave me ZERO skills to play live and understand basic music theory. The classical music approach was just notes on a page. On the other hand a guitar player learns chords, which teaches structure.
Problem #2 - The piano is just damn hard. I have a friend who plays bass, guitar and piano. He says that it would take him 6 months to be able (not good) to play bass in a band, 2 years on guitar and 5 years on piano. Think of it this way. Playing a chord in the right hand is like rhythm guitar, noodling notes on the right hand is soloing, or lead guitar (although you might try more than one note at a time). The left hand is the bass player, and the percussive nature of piano allows it be be the drums. To be a competent pianist you have to learn 3-4 instruments, and they all have to blend together. This is hard enough to do with just one instrument, let alone three+. I have been at my craft for 10 - 15 years and only feel that I am just starting to be able to put it all together.
Problem #3 - From my perusing keyboard forums, keyboardists find that many bands play too much and too loud. One of the jokes is never join a band with two guitarists, because there is no sonic room left. Yes just one electric guitar can annihilate, the sonic landscape, they have to be used judiciously. I know I feel that my bands often play way too loud. I am shocked when they can't hear me. They tell me to turn up, I tell them to turn down. Maybe us keyboard players are more introverted, non team players, who knows.
Problem #4 - Do we really have to play strings, sound FX, horns, organ, synth, piano, rhodes, etc. Why is it not the guitarists responsibility to play the horns? You can get a midi pickup for your guitar and use virtual instruments as a guitarist to play anything. Well to do this, as the post above suggests, we need to be computer nerds, fortunately I am one. Fortunately I can sing. But it always makes me laugh when I see a post looking for a keyboardist with all of these additional skills, like needs to be able to sing like freddy mercury and program a synth. Each skill in its own is an accomplishment, the combination is hitting the lottery.
Problem #5 - Maybe in our culture, we are loosing the focus on learning piano. In my opinion, it takes a minimum of about 10 years at 2 hours a day to be a competent pianist. With so many distractions, and other forms of entertainment, there maybe less kids coming up through the ranks. Why spend so much time when I can just rip a few chords and be a guitar hero? I am being somewhat, facetious, yes, but guitar or bass is probably more rewarding, with less work involved and our culture has moved more toward instant gratification and fame.
Combine all of the above and the end result is that you have 20 guitar players for every one keyboardist. And those that can "play" keyboard, probably are only good for one hand at a time. So they really aren't fully developed keyboard players.
Problem #6 - We want a challenge, Because a fully developed keyboard player, can be the bass, drums, rhythm and lead guitar, there is so much opportunity for us within a band. Yet often times, with many bands the keys just become an afterthought, and we don't want to have to just turn up to be heard. This leaves a talented keyboard player feeling bored in a typical band setting, unless there are some concrete challenging parts for the keyboardist. Then if you can sing on top of it, you don't even need a band.
As a side note, I do agree with getting a keyboard player that is new, and letting him grow. This does work, but only if the player invest lots of time.
As I said, I do not know the perspective of other musicians, so where I might be misguided, please feel free to correct me or add to the conversation.