eh, you have a point, but how much information do you really need to display in your signature? you can have all sorts of information in your profile, but your signature doesnt have to be your life story or anything, maybe just a catchy phrase or something. so i guess i'm sayin on one hand i see what you mean, but on the other i dont really think its necessary.
if nothing else, add a couple of words in your signature telling people to check your profile out. also, thats what AIM profiles are for, or subprofiles, or whatever you choose to do along those lines. i decided the aim profile didnt give enough space for whatever was on my mind at the moment, so i started a webpage.