Mr. Bennet disliked going out and only did it when nessisary. He doesn't seem intrested in public balls and only goes to the Netherfield Ball because it would have been rude not to. A married woman had no problems escorting un-married women to social events without her husband. This is one of the reasons that a young lady like Miss Darcy (who has no sisters or living mother) would have had a respectable widow as a companion.

]The O.N tells us Mr Bennet...(snip)..., gives him tickets for the Meryton Assembly