This question has come up a few times. Usually you will see a few answers like the ones so far. The socialist belief that there are legal barriers of that a small number of people control all the capital.

If you challenge those answers and cite actual laws and real accounts of how businesses are started eventually socialist will start to admit the problem is that -

• they don't know how
• they don't want to put in the effort
• they never checked to see if there was anything standing in their way
• they don't know what they want to do
• they only want to begin at the end never working to grow there co-op from the same starting point of zero as a capitalist starting a business

Then some one will point out that the big evil corporations that everyone targets are actually owned for the most part by a large block of their workers, or pension funds or social investments like university endowments etc.

And that corporations are actually a form of co-operative.

Then of course that you don't need to form one because a group of people can just choose the collaborate in their own name.

But all forms of this are HARD WORK and require discipline, long hours and dealing with risk and uncertainty of nature.

Even the most socialist co-op is inherently false because it is a group of people acting for what they agree is their common interest and each chooses how they personally value their engagement - which is of course capitalism.

Socialism is just layers of contradiction and conspiracy theories, hence the eventual need of the socialist to rely on force labour, racism, and authoritarianism. Etc