Why is Willy home?It is in Act 1 of the story
In Act I of Arthur Miller's Death of a Salesman there are plenty of small details that make up for a lot of foreshadowing and information that we come to find out later on in the play.
The first thing is that Willy, as your question states, returns home after what we suppose is a long day of work. Willy returns home late at night. It is late enough for his two adult sons, who are visiting, to be already asleep in bed. Linda, Willy's husband, comes out to greet him and immediately asks him whether he has had any accidents involving his car.
From the dialogue, we can tell that Willy is undergoing a lot of stress lately, that he has fallen asleep or gone distracted at the wheel, and that he has nearly been in accidents. This is what tells us right away that Willy travels long distances, even at his age of 63 where one supposes that he could be planning for his retirement and slowing down at work.
Therefore, Act I shows us how Willy Loman, still at 63, makes those long trips by car to destinations that seem to be more for his own entertainment than for actual business. This, we find out later, is because he is employed, but not producing commissions, at his insurance company. For this reason, his boss Howard allows Willy to go as he wishes, for he is not really needed in the New York office-or anywhere else to that effect.
However, even at Linda's requests for an easier position, Willy lies to her, and to himself, and tells her that he has to do those trips because he is the "New England man". This means that Willy, in his fantasy world, feels that he is vital to the New England customers and, that he has to make the long trips. At the end of the day, when he gets to his house (like he does in Act I) he is merely another older man who has not achieved his dreams, and who has to lie to himself about it in order to feel worthy.