In the story "A Rose for Emily," why does the father keep Emily isolated?

One of the key themes of this excellent story by William
Faulkner is the way in which blood or lineage is so important and can lead to a sense of
social superiority. It is clear that Emily Grierson represents an old, passing order of
time, and she feels that she is worthy of respect and special treatment because of her
social standing. The text tells us it is this sense of social superiority that leads her
father to keep her single, and it is this act that makes people begin to feel sorry for
her:

That was
when people had begun to feel really sorry for her. People in our town, remembering how
old lady Wyatt, her great-aunt, had gone completely crazy at last, believed that hte
Griersons held themselves a little too high for what they really were. None of the young
men were quite good enough for Miss Emily and
such.

Note the reference to
superiority and that Miss Emily was regarded as "too good" for the young men of her
society. We are then given the rather disturbing image of the father with the horsewhip,
preventing any suitors from seeing her daughter.