Nobody is forcing you to form a company. You can operate a business under your own name. Here in NZ it is called a 'sole proprietorship'. I'm sure it has its own name in the United States, but the fact remains. You can form a partnership with your other founders and operate as a partnership without forming a company. That's still how most law firms are structured, I believe. Doesn't require you to file anything or form anything or pay any fees, at least here and I expect also in the US. You want to go a step further, and take advantage of special legal rules. Those rules have a cost: you have to register a company.

Companies are creatures of statute. They do not come from the common law, or from custom. They didn't evolve naturally over time. They were invented. You can choose to form a company if you want the benefits that entails. But forming a company isn't free or completely painless. Still, it's a choice you get to make. Nobody can force you to form a company.

That being said, it does sound like it is a lot more complicated in the United States than it is here in New Zealand. Here the government tells you clearly how to do it, and it's pretty cheap and easy.

https://www.business.govt.nz/getting-started/choosing-the-ri...