If you're looking for the Hollywood take on the subject, dress shirts are worn without undershirts. The exceptions are uniformed actors (police, paramedics, fireman, military, etc. ) or period films (I think Clark Gable created a sensation and caused a "non t shirt" fad in a film, otherwise t shirts thru the 60's) or any film featuring Texas, IBM/school teacher/ professor or geeks.
Randy Quaid made a great statement for t shirts in 2 films. Who can forget the" black dickey thru the sweater" in Christmas Vacation or the beaming nipples in Kingpin.
