To say that they "gave up" suggests that they were at one point making an effort. I wonder if that is true. Perhaps they never made an effort in the first place.

We don't know, based on the evidence in the first nine chapters, but perhaps there will be evidence in future chapters.

I'm a little less sympathetic than you are to Mr. Bennet shirking his responsibility and hiding in his library. He uses his time outside of the library to stir up Mrs. Bennet's nerves, making the situation worse, and criticizing his daughters for characteristics that he must bear some responsibility for and that he is not doing anything about and perhaps never has.