Coming home is never a good experience for Biff. His parents' house is a place of tension and conflict, both spoken and unspoken. When Biff comes home, he must continually lie to his father in an attempt to deal with Willy's unrealistic expectations of Biff and his success in life. Willy pushes Biff, criticizes him, and cannot engage with his son in an honest conversation. Willy does not listen to Biff unless Biff is saying what Willy wants to hear.
Coming home reminds Biff of what a failure his life has become. It also reminds him of his failures while growing up. Most painfully, it reminds him of the time he found his father in a hotel room with another woman, which caused the irreparable break in their relationship. Biff and his father never discussed what happened in the hotel room, but neither ever forgot it. It lies between them always, unacknowledged but toxic nonetheless.
Each time Biff comes home, he leaves his parents' house after having another scathing argument with Willy. At the conclusion of the play, he tries to leave without another confrontation:
Everytime I've left it's been a fight that sent me out of here . . . . To hell with whose fault it is or anything like that . . . . Let's just wrap it up, heh?
Despite Biff's attempt leave in peace, a final emotional explosion occurs between them.