When people get old their mobility/independence/memory diminishes. To combat that they try to maintain a routine, a steady state. They fear change. Dynamic young people become scary unpredictable things. The answer is to exercise control in those areas over which you exercise effective control: finance and property. The natural extension of this control during life is to maintain control after one's death. That's what wills are all about.

Imagination also suffers with age. Old people that enjoy their later years want their kids to enjoy the same life... literally. So they leave the house to the daughter so that she can drop into her parents life. The parents cannot imagine that their daughter has her own perspective. They cannot imagine that the only reason the daughter even lives in town is to help take care of her wealthy parents, that the day after the funeral she will be on a plane to california.

That's right. It's a decision driven by emotion.