Another point of view is that the wage of the labor (eg. $5/hr) is a subjective amount coming from the negociation between the employer and the employee, and consequently their respective bargaining power. So, for some jobs, the real wage is not $10 or even $5/hr, it is effectively "the lowest amount law let an employer pay someone", due to the dramatically unbalanced negociation. In this view, minimum wages protect the poorest and most exploitable job seekers from having to accept whatever the employer with full bargaining power is willing to concede. Of course, not everyone subscribe to it and it comes with its own problems too, but it is still an important part of the debate, in my opinion.