Originally Posted by ckcowl

SO, THAT IS THE REASON! YOU GET BETTER SEAMS...why are you looking for more? reading through the responses everyone has pretty much told you the same thing...the reason to set your seams is so you have smoother, better looking seams when you then press them to one side or open...that IS THE REASON...so, you are still asking why????
WHY???
sometimes (especially when you are fairly new) people tend to try to over-complicate things...it does not have to be complicated...it can really and truely be a simple reason. don't try to feed more into technique's than what is already there. it is a simple thing. set your seams and you will have smoother seams....
no reason for stress...