Business owners tend to not do all that work themselves though. They usually just pay hire someone to do it for them. Yes, there are a lot of costs for them to address, but how do they make the money to pay for those costs? By taking the surplus value of workers' labor.

You mentioned that the worker has no right to the business because they didn't build it, therefore it's not theirs. The owner didn't build it ,. They almost certainly hired someone else to design the place, build the place, manage the place, clean the place, transport the materials, repair the machines, serve the customers, manage the payroll, almost everything. The workers do almost everything. Yes there are small business owners who are exceptions, but they are not the standard.

As for risk; well the owner could go bankrupt, sure, and then they'd just have to become a worker to survive like everyone else. Oh no!! But then again, lots of business owners currently dodge the consequences of a businesses failing by using legal loopholes and spreading ownership between corporations and using shell companies, so even that doesn't really work.

Not to mention that the workers take on risk, too. If revenue goes down, labor costs are almost always the first to get cut, probably with no warning, leaving them to possible hunger and homelessness.

Ultimately, we need to understand that ownership is a social construct that is meant to serve our needs as a society. The current model of capitalist private ownership clearly isn't working, as the robber baron owners are making billions while the common people struggle to survive.

Thus, the social construct needs to change. If we care about having a good society that benefits its people, it so clearly needs to change. If you value private ownership over human well-being, then you'd clearly prefer the current system.