Why the distinction? Because this work involved Photoshop and mine used emacs?
It is only available to freelancers. People working in those fields usually don't have the option of regular employment. For that reason was decided that companies using their work still need to contribute to health insurance (as all regular employers need to do as well). For everybody else the answer is: seek regular employment if you want someone else to pay half of your health insurance.
Still does not explain why there is a distinction. Why do artists get to have companies paying them part of their social security while other freelancers still need to make this out of their own pocket? If this is a good idea for the artists, why not for other professions?