Our current system of law is the least worst to date.

It sucks... but everything else we've tried sucks worse.

Old joke: How are lawyers like nuclear weapons? If one side has one, the other side has to get one. Once launched, they cannot be recalled. When they land, they screw up everything forever.

Until you need one

You only need one because someone else uses one against you, and the law was written by lawyers in language only they can understand ;) Thus, in the hypothetical scenario of no lawyers having existed, either they would be replaced by some other ruling and representative class, or the problems they solve wouldn't have been invented in the first place.

Instead, the Hatfields and the McCoys just kill each others sons for a couple dozen years.

The problems are human nature. Lawyering is often childish, uncivilized and brutish, but we are making progress.

Often, lawyers help keep someone from being against you. In contact law, lawyers are there to make keep a dispute from happening. A good lawyer will be able to foresee a potential problem and make sure you negotiate it's outcome before you enter into a deal.