One reason is this outstanding quote.
Elizabeth Bennet: Are you too proud Mr. Darcy? And would you consider pride a fault or a virtue?
Mr. Darcy: That I couldn't say.
Elizabeth Bennet: Because we're doing our best to find a fault in you.
Mr. Darcy: Maybe it's that I find it hard to forgive the follies and vices of others, or their offenses against me. My good opinion, once lost, is lost forever.