Having a life not driven by necessities is pretty big a privilege.

No, I don't think so. See e.g. this.

Also note that you're coming from the region tainted with Weber's Protestant work ethic X-)

being driven by necessities is pretty normal and I don't really understand why should it be a mental illness

Depression isn't about being driven by necessities. In this particular context "not having desires" is the important part. I understand that from the Buddhist point of view that's entirely backwards :-)