It should be remembered that, for Willy, history repeats itself. Willy was abandoned by his father and older brother when he was little:
WILLY (pulling Ben away from her impatiently): Where is Dad? Didn’t you follow him? How did you get started?
BEN: Well, I don’t know how much you remember.
WILLY: Well, I was just a baby, of course, only three or four years old...
BEN: Three years and eleven months.
WILLY: What a memory, Ben!
BEN: I have many enterprises, William, and I have never kept books.
WILLY: I remember I was sitting under the wagon in — was it Nebraska?
BEN: It was South Dakota, and I gave you a bunch of wild flowers.
WILLY: I remember you walking away down some open road.
BEN (laughing): I was going to find Father in Alaska.
WILLY: Where is he?
BEN: At that age I had a very faulty view of geography, William. I discovered after a few days that I was heading due south, so instead of Alaska, I ended up in Alaska.
Willy's father made and sold flutes. He too was a traveling salesman. Thus, that Willy spent so much of his time on the road is not surprising at all. Compared to his father and brother, however, Willy was much more of a family man, absent for long periods of time though he may have been.
His infidelity can not be so easily explained, but it, too, may stem from his early abandonment. As Willy says to Ben:
WILLY (longingly): Can’t you stay a few days? You’re just what I need, Ben, because I — I have a fine position here, but I — well, Dad left when I was such a baby and I never had a chance to talk to him and I still feel — kind of temporary about myself.
What a sad admission to com from a grown man.
Yes. There is betrayal and abandonment but it is much more deep and multidimensional than what it looks.
The most obvious betrayal came from Willy Loman to his wife, as he took a mistress earlier in the storyline. The betrayal is not only the fact that he was a cheat, but that he also bought stockings for her, which were very expensive, while his wife had to mend her own. This is particularly what struck Biff the hardest when he found out about it.
The abandonment comes from many sides: There is self-abandonment, the abandonment of the family unit (which led to the high dysfunction at the Lomans), the abandonment of hopes (as the American Dream died and memories took its place), and the final abandonment that came when Willy committed suicide. The latter is not so much abandonment, but actually the death of the dream in itself, however, it was yet another separation of Willy from his family, this time to a journey he will never return from.