Stock Rod Limitations?

One thing I've heard time and time again from machinist's is that it's not worth rebuilding the stock rod,because the new ones are so cheap.Weird. I'd think the machinist would want the work? And I cant really see thier point either,as a new rod is somewhat of an unknown compared to a proven piece like the stock mopar rod.I see thier point when it comes to chevie,as g.m is junk anyways.