However, there are systems which 'don't allow' the rampant levels of inequality that we have now, in the same way that capitalism 'doesn't allow' for every working person to become a wealthy CEO. Unfortunately, since the red scare, these systems have been absent from the American consciousness. Though, recently they are starting to repopularize.
When there is an abundance of labour supply and re-training requires huge capital, there's little difference between capitalism and slavery from the labourer's perspective.
But they are, especially in low-wage or tipped shift work. People are kept under unethical and often illegal rules, pointing out that they're illegal will probably get you fired, and even holding a second job to make ends meet might end up with you being fired from one or the other if both your bosses decide they need you in on a certain shift. The idea of "self-ownership" only applies insofar as you can find someone else who will hire you (likely under very similar terms to your current job - i.e. under constant threat of being fired) for most people.
As people generally in a skilled job with some savings, most people on this site are somewhat buffered from the realities of what a lot of people across most of the world, including their own countries, have to deal with.
Interestingly, in Seattle, with the 15/hr movement, initially businesses were using small business as a shield to argue that 15/hr was unsustainable. Unsurprisingly, they quickly changed their tune when we said that we would levy greater taxes on larger corporations to subsidize small business.
These reasons, among many others, is why I'm involved in 15 Now and other fight for 15/hr minimum wage that's pegged to inflation. Capitalism is increasingly unstable. People continue gaining consciousness of this fact.