I think keyboards/pianos are the most beautiful instrument around. Once you learn the keyboards, it's quite easy to pick up any other instruments because ur knowledge, ur theory is there...although the concept of virbrato and bends can be quite mind boggling for awhile!
I don't agree that keyboard can't be "showman". But it's not the same as guitar dudes. Keyboardist "showmanship" is with the same class as the drummer IMHO. They are both fixed in one position but they can still dazzle the audience with their skill and movements..etc I think showmanship doesn't mean only jumping around. Take Sonata Artica for exmaple, the keyboardist places his keyboards facing forward instead of upwards so that the audience can see his fingers fly...sometimes he straddles the keyboard too.
One stumbling block about pianos/keyboards is the cost of everything! It's just so damn ex!! If you want a good system running, be prepared to fork up to 10k... if you are ok with low end stuff...I think u still need to fork out 2k+. With that amount of money, I can get a good amp, a relatively good guitar and some effects to boot.
I think guitars are popular because they are versatile and it is easy to learn it's basics. Can sing and strum... most emo/pop songs only require you to learn power chords...then with distortion, ezy, don't even have to play it well to jam. Keyboards require much more skill to perform well.
But to be fair, guitars are not "that" easy as well. If you take the classical route, thats about 5 to 7 years for the grade 8, a few more years for the diploma/degree. Mastery calls for total dedication most of the time, if a guitarist wants to reproduce those pieces played by pianos, then really have to sit down and concentrate....(not simply blaze through monophonic style like Yngwie but polyphonic style)