Gus, summer heats excluded, I always wear shirts as base layers, below knitwear or jackets. This was their original use and still best serves them. After all, shirt fabrics never drape like cloths so they must sit close to the body to look clean, but this doesn't well serve men with guts, poor posture or askew shoulders. With movement the hem will rise up from the trous and pile up, and the shirting will crease sooner or later. For these reasons, the shirt works best under other garments -- no matter how clean or close its cut.
Good point. I also almost exclusively wear my dress shirts with a suit or sports jacket so i do like it to fit close