You seriously dont believe that wealthy employers will not exploit to the last drop of blood a situation where they can pay the least wage possible to workers who have no welfare or union support?

Look at history- Victorian England where all this started in the context of the modern industrialised economy.

Look at the 'developing' world where this is still almost universally the case. Look at the 'developed' world where minimum wages are almost universally in place and where extreme poverty and labour exploitation is very limited via the combination of minimum wages and welfare.

As @Undisciplined as pointed out where both strong unions and strong welfare provision are in place a minimum wage may not be required...but otherwise where it is not present employers will universally and quite logically exploit their position of relative advantage and do so ruthlessly.

Where there are no minimum wages there are huge disparities between the wealthiest and the lowest income citizens. Thus has been shown to reduce the overall performance of the economy- why? Because people living in abject poverty seldom develop their innate human capital potential to the maximum. They cannot afford decent education, training or even to travel to somewhere with a fairer economic paradigm. Meanwhile the very wealthy control the political system and entrench their privilege with no regard for the wider harm to the economy and society. Many nations fit this description and do not need to be named.