Whether all people do it or not is another question, but that is what is required by the law.
What you might need a company for is to pay sales taxes you charge for physical goods, or get insurance appropriate for your line of work. That's likely to be state-by-state. You just get the convenience of an EIN by registering and some additional legal protections by being a distinct entity (i.e. I could sell the company or assign IP to it or hire employees).
I have certainly gotten contractor income to me personally that I just had to account for. In the USA for small businesses you'd have to send the same documentation, so it doesn't even save paperwork. As a sole proprietorship I get the same tax documents from my clients as I would if I were operating directly under my name.
Edit: Also, if this were true in the USA, it implies that all those Uber drivers each have a sole-proprietorship set up. I'm pretty sure that companies can hire contractors as individuals without them becoming businesses.
No it isn't... In Canada, you can happily accept money from people and just stick it in the "other income" box on your tax return, where it'll get income-taxed appropriately.
If you're trying to do business deductions or want to pay business taxes instead, yes you need a business. If you're trying to set up a physical location, yes you need a business license from your city. But if you don't care about the pennies and your work is digital there's absolutely no requirement.
This is not the case in the USA. There is no general federal legal requirement to register a business or obtain a business license in order to sell things. However, there are specific industries for which business licenses are required (at any of the federal, state and local levels) and forming an LLC might help personal assets if you are sued.
