Good point about second proposals. I'd guess that reluctance to make them would, at least in part, be caused by injured male pride - if a woman has turned you down once you risk looking like a wimp(in modern parlance) if you try again.

Since Wentworth was so deeply in love with Anne, he would also be wary of setting himself up for a second dose of pain and disappointment. The way he had dealt with her rejection, by stigmatising her "feebleness of character,..... weakness and timidity", must have created an additional barrier to him making a second attempt.

That said, I still think he should have gone back to try again after a couple of years when he had made some money, given that his lack of money was the main reason why Anne had ended their engagement. Also, Anne was 19 when they were engaged. A couple of years later she would have been 21 and legally an adult so parental consent to her marriage would not have been strictly necessary.