Ah but what about the grain?
At the heart of socialism lies its contradiction with rational behaviour. To introduce a socialistic system requires that humans stop behaving like humans. Capitalism, on the other hand, is aligned with how we think. It is in tune with evolution, it harmonises with the struggle for improvement; it is sympathetic to our emotions.
When the first humans walked out of Africa they weren't practicing socialism; they were looking for advantage, for a better life. As their wanderings took them from place to place they didn't negotiate on the basis of need and equity, they out-competed whoever was there before them. They were by any definition free marketeers, they were capitalists.
A centrally planned economy could work in a world where there was no scarcity and where all choices/preferences were aligned. Until then socialism will always be cross-grained relying on compulsion for its survival as a system of government.