There have actually been a few cases that have made it through the courts that apply "employee" status based on how the company treats the worker rather than how they're paid.
Especially in cases where the worker is on long-term assignment somewhere like Google.
Maybe not "need", but yes, a fully peer reviewed study confirming or rejecting seemingly obvious conclusions is an important part of the scientific method. It's how we gain confidence in what we (think we) know.