I partially agree with you, but I'd point out that you often need a fine arts degree ("Illustrator" or "Graphics designer" typically being concentrations pursued in the course of such a degree) in order to be considered qualified to teach it. You're correct that it probably doesn't help you in terms of selling artwork, but it is essential if you're looking for a job in that field.
As for sociology, if you want a master's degree or PhD in sociology, an undergraduate sociology degree is a much more direct path to such a program than a degree in psychology or anything else, and there is a significant body of literature that a graduate-level sociology student will be expected to be familiar with that most likely s/he will not be exposed to in other disciplines.
I guess my point is that the value of a particular degree is highly dependent on what you actually intend to do with it - if you aren't intending to work in a specific field where you know (by actually looking at job listings) that your specific degree is required (or is a step along one of the direct routes there), there's no reason to get it. And in general, if you are intending to pursue an entrepreneurial path, then any degree at all is mostly useless. Clients and customers care more about feedback from other people who've handed you money before than they do about your educational pedigree.
And really, the whole conversation feels a little silly considering that the evidence is mounting that the value of human labor as a whole is on a downtrend that is unlikely to recover, both in terms of population pressures and automation/AI pressures. My advice to my friends and their children, speaking as someone with a master's degree from a global top-ten university, is that it's only really worthwhile in two cases: 1) if you can get it for free or very near it (scholarships, rich family, etc.), or 2) you're one of those unusually driven people who knows exactly what you want to do with your life and will sacrifice anything, including creature comforts, to get it (since you'll be paying off student loans for years, particularly if what you're driven to do isn't high-paying). I strongly believe that the obsession with educational choices, millennials and their work habits, etc. are all primarily side effects of America's refusal to recognize that the future of work looks pretty bleak and that we need to rethink the means by which basic resources are provided - it's highly unlikely that there will ever be "enough" jobs again, so we need to consider what to do with people who just don't really cut it in terms of productivity and how we want to treat them as a society.