well..for something that is mass produced...there's always some miss-produced measurement....
altough not significant in a glance..ppl who chase big power+drivability need fine tuning....
this is one of the area that need to look carefully.....as example on bike's engine head,mine can plonk in any type of camshaft and still got space for the cam lobe to rotate freely.....but some of my colleague's bike have trouble where to install exactly the same camshaft in different engine head(same bike model)....we need to grind the internal space for camshaft to allow it rotate freely....thats small example on casted product....(wouldn't happen on precision machined product).....so there's always room for improvement....