If your goal is to, say, kill all of the tigers in the world, why would you be okay with making more baby tigers? Yeah the baby tigers are cute and can't hurt anyone yet, but baby tigers don't stay babies for long, and 100% of the large, angry tigers who like to eat people used to be baby tigers.
The goal of communism is not to turn every person into a capitalist, it's to create a society/economy that meets the needs of all of its members instead of just those of the rich. Encouraging the working class to start businesses is just like making more baby tigers: it's working in the opposite direction of your goal.