Capitalism creates profit. Socialist systems don't create profit.
Labour is certainly part of the profit-creating system. But labour alone isn't enough to generate profit. People laboured intensely in Soviet work camps, worked themselves to death, and yet the Soviet system didn't work. They didn't make profit on the free market.
On the other hand, hard workers thrive and help the economies of capitalist countries such as Japan and South Korea thrive.
And, in many ways, what's so unfair about the way wealth is distributed now?
What would happen if people at the top of the pile were paid as low as manual labourers? The Talent would sod off to another country that paid them higher.
I'm poor. I'm poor because I've got a lazy streak and I haven't got myself a decent job so far. It sounds harsh but it actually seems fair to me, if I'm being honest.
However, if I apply myself, I could get a decent job and career. Because I live in a capitalist country.