About Mr Bennet not saving money for the future..

I am afraid some of the women in the family tended to be very lavish, and made it impossible for him to save (well, he could have, had he tried to exert authority on his wife instead of retiring in his library)...
An example of this can be taken from the horses (see some threads further down) which he would like "in the farm much oftener than I can get them"... The horses are probably used for the carriage quite often by Mrs B and her daughters, who unlike Lizzie may not like the effort of walking, therefore making the farm less profitable than it could otherwise be.
Let's wait for the next weeks to have some more confirmation on the expenses incurrend by some members of the family.