nate
***** Our company mechanic, with whom I worked for several years, very often did not have the rotors machined when he re-padded a car. He could tell - by eye- if the rotor was damaged enough to require machining, and I'll have to say that he got it right approaching 100% of the time.
If I ran a shop, I would - to keep my business and conscience clean - probably resurface every rotor that came in and could take a cut. Resurface can take on several levels of involvement.
On my own cars, I machine them if I see that they need machining. Just like you do, I imagine.