Some people are just afraid.
I had a guy tell me that after paying $600 for a engine and muffler he expected it to be "RIGHT"
I told him it was right, for the guy who ran and tested it.
Unless you live in the same location and tested it in the same set up then you need to adjust the engine.
I also see people who want the very last RPM out of the engine.
I just tell them to adjust it until the engine two cycles at WOT then leave it.