Once again, it’s a question of each to his own, according to his own tastes and needs. Generally speaking, it’s considered more elegant, and more formal, to do without pockets on a shirt. Nevertheless, for everyday shirts that you wear at work, a pocket can be useful. On the weekend or for shirts with a “gentleman farmer” look, the pocket suits the shirt well. You can even opt for two pockets, and why not choose a model with a flap or epaulettes for a military look?
By the way, custom suggests that pockets are de rigeur on causal shirts with button-down collars, such as a classic button down collar, an American button down collar, a Portofino collar, or a tab button-down collar)