Lawyers in criminal cases generally work on a fixed fee basis, so working needless hours on one client means less work they can do on other clients. Celebrity lawyers charge hourly, but that is because their clients are so much more demanding that they generally only work on a single client's case at a time.

Lawyers in tort cases bill on a contingency basis, so working more does not change their payout--success is all that matters.

Lawyers in transactional cases usually bill hourly, because when you're talking about multi-million or multi-billion dollar transactions, the few thousand you spend on the lawyers and accountants is a rounding error compared to what you spend on the airfare for the executives negotiating the deal.