And since (1) We're talking about people already adjudicated guilty, and (2) almost always NOT the party paying the lawyer there is no real incentive for the lawyer to win, just to present a credible (Professional) case.

Even if only a small percentage of prisoners seeking parole pay for their own lawyers, that still constitutes a market whose participants have the incentive to figure out the informal intricacies of parole hearings and adapt to them.