"not sure if I am mildly annoyed, or mildly amused, when a performer does not even get his guitar out the case till he is on, and then decides to tune up."

What setting are you in? Certainly not Concert or Festival. Singaround, or session in a crowded room perhaps? Tuning on stage is common because of the vastly different temperature changes that exist between backstage areas and "on stage" under a full festival or concert lighting rig.