Because the client is generally more concerned with getting a favorable outcome in the lawsuit than on the fee and a lawyer willing to charge a smaller fee is a

Because the client is generally more concerned with getting a favorable outcome in the lawsuit than on the fee and a lawyer willing to charge a smaller fee is a signal that they will be less likely to achieve a favorable outcome. It's the same reason that you don't see a lot of price competition for real estate brokers (though this is changing some). I'm not saying this is a great reason, but I do thin it is the reason.