SL - some good and pertinent questions. (And yes, I should change the thread title to 'playing corridors" - although these are/were the functional equivalent of fairways) If, as conventional wisdom would have it, the rationale for width was related to the wind (and perhaps the wind's effect on a then-new golf ball) and on some early ideals about options and fairness and strategic interest, I would imagine that a) someone, somewhere, at some time would have made the connection/rationale explicit, in print, and b) that if it had been made explicit, in print, by one of the early masters of the craft, we just might be having the very discussion you allude to about fairway width in an era when the golf ball, off the driver, spins basically not at all (even for a straw-man like me, i.e. an average golfer).
Peter