Superheroes are very much 'in' at the moment. You almost certainly went to the movie theater to check out 'Avengers: Endgame,' and so did we. Out of the whole pantheon of superheroes who were on the big screen during that film, everyone has their own favorite. This guy clearly has a thing for Captain America. We get that; what's not to like? He's a charismatic, patriotic guy who loves his country and fights back against the forces of evil.
Even Captain America has a life to lead, and that life means stocking up on supplies whenever it's necessary to do so. Maybe he's exhausted from a full day of battling bad guys, and he's headed straight from his day job to pick up a snack without stopping off to get changed first. The icing on the cake is the pair of glasses he's wearing on the outside of his mask. At least it will have brightened the cashier's day.