Oh yes, I forgot about cent accounts - that's what brokers that allow trading with tiny deposits are often called. It is a good way of practicing, a great next step after a demo account, but it is indeed not much for making profit.
It is important for determining the position size before placing an order. This allows traders to calculate risks, profits and minimise the risks.
Lower the position size, lower is the risk.
Minimum investment is the best option for beginners to start trading live. They can prefer trading on either cent or micro accounts. This will not only help them to adapt to the live trading environment but also help in developing trading psychology.