He wouldnt which means one of two things: 1) the fact that his client will lose is not as sure as you think or 2) he doesnt have control over his client (meaning the client is going against his advice to settle). Settlement is the clients decision, not the attorney.
If there is no agreement between the parties then the only option is a trial.
I have been a criminal attorney in New York for almost 25 years. website: Brooklynlaw.net Phone #: 718-208-6094 email: email@example.com. This answer is only for informational purposes and is not meant as legal advice.
Generally speaking, he wouldnt go to trial knowing he'd lose. The certainty of losing or winning is not known. If the party doesn't want to go to trial, the attorney wouldn't go to trial.
Perhaps the attorney is not convinced that he will lose. It could also mean that the client is not interested in settling and so the attorney has no choice but to go to trial. Absent a settlement, trial is the only other option.
Deciding to try a case is not the attorney's decision. The attorney's job is to inform the client of the liklihood of success based upon the law. Ultimately, the client dictates whether a settlement offer is acceptable.