Why would anyone work at a business if they can't own at least a part of it or have any control over the work they do?

A business takes more than one guy to run. Instead of one guy deciding to start a business, having to raise the capital to do so (which usually means they don't totally own it) and then employing people to control and exploit, all the people who would work there can get together and decide to start it together and own and control it together.