I guess you never purchase anything mechanical as new? Everything mechanical has a break in period. Parts are going to wear together. Ever buy a new car? Everyone that I have purchased has directions on how to drive it for the first 500 mile break in.

How about shoes? Ever buy new shoes and the get more comfortable the longer you wear them as they start to form to your foot?

Same is true with a firearm. I wouldn't take a new pistol and carry it without cleaning it and firing a few hundred rounds through it to insure proper function. Mass produced firearms are not hand fitted. Those moving parts need a break in period to insure that they wear together. It is not uncommon to see wear marks and peening after a firing a couple boxes of ammo through a new firearm where the moving parts have settled in together.