In NL, UK and probably Germany there is a plague of "freelance" developers and indeed also physicians that work full-time for the same companies for multiple years. In my opinion, it's fine to raise taxes on those kinds of freelancer/employer relations to the same level as salaried employees.

I see my own services as very different. You call me when you need short-term & part-time help to solve a problem or bootstrap something within your own company. Doing that in a long-term salaried position would not make sense.

Curious to see what will happen over the next years!