Imagine the paradigm - the employer goes to the tavern and hires some “heroes”, guys in a bar happy to risk their lives for money. Who do you get doing that? You get crap, people who cannot be trusted. Typically these are at best inexperienced folks, guys who would be just as likely to steal the prize or sell the employer’s secrets.
What do we do in real life? We do interviews with references and/or make use of recruiters who are expected to know the candidates. Using a recruiter makes a whole lot of sense. It makes a lot more sense to have an experienced warrior go out and form a team for you. He will know other warriors and may know other adventuring types as well. Far better to let him make the decisions. While he may not know them personally, he will have a much better chance of at least gauging their abilities.
In my campaigns, we've used recruiting posters and guilds, but for the best results, use a recruiter. In a recent campaign by one of our younger game masters, everyone in the party was a skilled missile user, but the bad guys were goblins living in a twisty cavern system. There was no hope of using missiles. A recruiter would have done a better job of putting a team together.