it would appear that the OP hasn’t yet had the time lifting to have answered it for themself, so I think it’s a valid beginner question. (though the answer could have easily been actually researched in articles rather than just taking the lazy route of asking).
X summed it up well - no single exercise can hit all parts of a muscle effectively enough to create a balanced physique. so, beating the piss out of yourself with one exercise would probably just limit your ability to recover, and you’d end up out of proportion and probably wind up with some ugly muscle imbalances that would potentially lead to injuries down the road.
i hope that helps, without unnecessarily making you feel like an ass for asking. (though, really, do some research next time - there’s a lot of good articles here that will answer most of your questions)
Thanks for the non-abusive answer. As for Prof X, I fully appreciate the fact that you’re one of the most knowledgeable, experienced and developed posters on this site, so it saddens me that you take this attitude towards someone innocently asking a question.
Returning back to the point though, how come people don’t just end up doing 1 set in each of 15 or so exercises (ie. variations in hand position, width, angle, movement plane etc) for a workout?
Edit- sorry if I’ve misinterpreted your tone.
Because there’s next to no neurological adaptation to the movent patterns used, and next to no progression on load per movement. From other angle, do you think you’re gonna have at least a decent level of intensity on 15 sets (there’s no point on doing those exercises for hypertrophy and 1 set if not taken to failure)?
Man, from my experience, one “guru” told me once “I don’t get why you make lateral elevations, bent over raises and all that for shoulders, its just one muscle…”, as pathetic as it may or may not sound to someone, guess how the guy looked?