The answer can be found in Act I when Biff and Happy speak together about their lives, and Biff in particular comments upon how he has led his life up until this stage, and the reason why he has had so many different jobs and always ends up coming back home. Note what he says to Happy about his last job:
Hap, I've had twenty or thirty different kinds of jobs since I left home before the war, and it always turns out the same. I just relaised it lately. In Nebraska when I herded cattle, and the Dakotas, and Arizona, and now in Texas. It's why I came home now, I guess, because I realised it. This farm I work on, it's spring there now, see? And they've got about fifteen new colts. There's nothing more inspiring or--beautiful than the sight of a mare and a new colt. And it's cool there now, see? Texas is cool now, and it's spring. And whenever spring comes to where I am, I suddenly get the feeling, my God, I'm not gettin' anywhere! What the hell am I doing, playing around with horses, twenty-eight dollars a week!
Thus we can see that Biff came home, as he sees to come home every time from one of his various jobs, because he feels that he should be "making his future" and making something of himself in a respectable position where he can earn a decent living, rather than working as a hired hand. We can see with this comment the way that his father's teaching has influenced him. He is unable to be satisfied in a job that pleases him and he loves because he is always fixated on making it big in life, somehow.