There is a purpose for casual/contract labor. If I want my lawn mowed, some basement junk hauled away, or my house painted, I want someone on contract/gig to do something for me, but I sure don’t want to hire an employee.
How that person chooses to relate to an employer (whether to be self-employed or work for someone else) is their business, not a concern of mine.
However, from a policy standpoint, I certainly don’t want to prohibit them from being a solo entrepreneur or similar.
So, there’s a reason to allow contract work, even with individuals. Whether you extend that to Uber transportation or to Uber’s new business is a fair question, but “employ them” is not the universal answer to Uber and non-Uber.