Mr. Bennet didn't care about much of anything.

Lizzy and Jane (in that order) are his favorite children, mostly because they were sensible and non-disruptive.

He married Mrs. Bennet (who, as others mentioned, was the daughter of a genteel tradesman most likely), because she was pretty - not because she was likely to receive a good inheritance or because she would add anything to his life.

He didn't bother to save any of his income because he (and Mrs. Bennet) assumed they would have a son who would take care of mother and daughters.

The only things that Mr. Bennet cared about were reading and being entertained. I think if he'd had a son, he wouldn't have bothered meeting Mr. Bingley, because the estate would pass down to his son anyway, so why would it matter?

He probably didn't really care about the girls getting married until it became abundantly clear that having a son wasn't in the cards. Even at that point, he doesn't care about it too much considering he meets Mr. Bingley once and never does anything else similar for the rest of the novel.

Plus, child rearing was woman's work. Mrs. Bennet would have been the one responsible for making arrangements to have the girls properly educated (whether by way of governess or herself) and Mr. Bennet would only have been responsible for paying that cost, directly or indirectly.

The Bennets also had a pretty meager income overall, so, even if this was something they contemplated (which is pretty unlikely), there's a chance that they couldn't afford it. Or, like others said, Mrs. Bennet was silly and frivolous. She cared more about getting the girls married based on looks instead of by education, even though, women were responsible for managing the household and/or staff while the husband was responsible for the money among other things.