Market-based wages tend to promote unfair working wages. With a free market, employers can pay their employees as they deem fit. Unfortunately, this can lead to employers taking advantage of their employees.
A free-market economy – one unfettered by government regulation – can promote unfair working wages. Without any form of the government-enforced minimum wage, employers can pay their employees how they deem fit. This occurred in the United States during the Industrial Revolution. Business tycoons of that era (like Andrew Carnegie and John Rockefeller) paid their employees an unlivable wage. They could get away with this because there was no check to guide the market. This led to the formation of labor unions – organizations meant to protect the workers from employer mistreatment. The entire labor movement in the United States of America came about due to unfair wages that a free market (a major portion of the political philosophy Liberalism) allowed.
There are many reasons why market-based wages are positive. First, they are not some arbitrary number of acceptable wages across all industries. Market-based wages pay employees fairly for their work, determined by the supply and demand of that industry. Additionally, a one-size-fits-all approach naturally leaves some people underpaid. This would not fix unfair wages. Another argument against a universal minimum wage is that they are costly to taxpayers who have to foot the bill for oversight and enforcement. Market wages do not require such oversight and are, therefore, less costly. Universal minimum wages reduce competition and desire to work hard, leading to an overreliance on the government to solve all problems.