Thanks for all the responses. There are some interesting comments here. Let me ask you this then...
How many easily identifiable musicians (guitar, bass, drums only) do you know that have drastically different sounds from song to song?
Keith Richards sound was pretty consistent from song to song, wouldn't you think, with only minor effect changes?
Another point; synth sound selection.
Like so many other great musicians, Van Halen, Phil Collins, and so forth, all have a very unique, unchanging sound. You knew who you were listening too, even if the new song you are just hearing was played unannounced. My approach to playing synths is similar to that. I wanted a small cache of sounds (with minor variants only) to serve as a way of making me more identifiable as a synth player.
My chosen sounds are somewhat dated. I love the sounds of the older analog keyboards. These can only make use of saw, square, and pulse waves (some could do more). One can only add a high pass, or a low pass filter to them, adjust cutoff frequency and resonance, add low frequency oscillation and a volume envelope to them.
Newer synths are more like emulators. They use actual samples or physical modelling to approximate the sounds of things like horns, pianos and flutes, as well as other-worldly sounds.
I've always thought that if you want horns in a song, hire a horn player. I'm not into the replication of other real instruments, but rather the old, fat and warm, analog pads. I even turn off velocity sensitivity and after-touch on my JP-50 because most of my older analogs don't have either one.
So basically, I use my core sounds on purpose for reason of musical identity and consistency across songs, just as a guitarist or bassist would.
I guess that's the real point of this; why do most bands just expect us to run the gamut, instead of allowing us our own identity, even if we aren't front and center?