I guess, but those pockets existed with much smaller scale production. There's no profit to be had by small firms when socialist production would have outcompeted them. Also why would workers choose to work for a capitalist for less pay?

There's also the fact that capitalism and communism are directly antagonistic to each other while feudalism can work alongside capitalism. Hell primitive accumulation and enclosure is the direct doing of feudal lords abandoning the old feudal contracts and choosing to become capitalist.