Somewhere along the line, I think the role of economics would have entered into it. In the Annie Proulx story, the old man has a line that didn't make it into the screenplay: "I can't get no help out here." It might be interesting to see him deal with the conflict between his disdain for his son and his probable dislike of Ennis on the one hand, and, on the other hand, the fact that he suddenly has two healthy, strappin' young fellas to run his ranch for him and maybe turn the place around.
"I can't get no help out here" was a rather interesting thing for John Twist to say.
In the book, Jack father actually said that AFTER Jack's mother said,
"He used a come home every year, even after he was married and down in Texas, and help his daddy on the ranch for a week fix the gates and mow and all. I kept his room like it was when he was a boy and I think he appreciated that. You are welcome to go up in his room if you want."Mrs. Twist had mentioned to Ennis that Jack did go up to Lightning Flat to the ranch every year and help his daddy; but, his old man talked like Jack never even showed up. Jack apparently worked hard as much as he could to get his father to accept him by working with him and his father still was not pleased.
As far as the story goes, since Jack never worked for his father-in-law when Lureen's old man was alive, it probably was somewhat expensive for Jack to make a trip up to Wyoming every year to help his father. According to what Annie Proulx wrote, it was quite a while, or at least seems to be, after Ennis had Thanksgiving dinner with his daughters, Alma and her grocer husband, before Lureen's father died.