This is a very common and very misinformed opinion.  The problem is that not all jobs are created equal.  Workers are a commodity, and the value placed on the wage associated with a given job should be commensurate with the value of the work.

Therefore, low-skill, high volatility and turnover work will always pay less, and deservedly so.  In no way is it the employer's responsibility to take any factors other than the value of the work into account when determining an appropriate wage.