Have you noticed how often Frank is late? It seems like there is always some anxiety over his comings and goings.

Of course, within the plot of the novel, his aunt causes most of it, but why do you suppose Austen makes it that way?

In chapter 37, Mr. Weston says about having Frank in Richmond,

Now, it would be really having Frank in their neighbourhood. What were nine miles to a young man? An hour's ride. He would be always coming over. The difference in that respect of Richmond and London was enough to make the whole difference of seeing him always and seeing him never. Sixteen miles -- nay, eighteen -- it must be full eighteen to Manchester-street -- was a serious obstacle. Were he ever able to get away, the day would be spent in coming and returning. There was no comfort in having him in London; he might as well be at Enscombe; but Richmond was the very distance for easy intercourse. Better than nearer!

Even when he is on time to his father's ball, there are all these jitters: "Frank was standing by [Emma], but not steadily; there was a restlessness, which showed a mind not at ease. He was looking about, he was going to the door, he was watching for the sound of other carriages, -- impatient to begin, or afraid of being always near her."

And, of course, his extreme lateness at Donwell has Mrs. Weston coming looking out for him incessantly. It seems like nothing can really be settled until his whereabouts are determined, and even then he is often where one would not expect him to be, like rescuing Harriet from gipsies.