I saw the New School in NY has a PhD in aesthetics… which would seem likely to end any debate with sales or marketing 
I agree with Cyber, design is not really an academic activity. You learn much more in apprenticeship type situations with good mentors on the job. If you aren’t working with real projects it is all rather fictional and the experience doesn’t translate. Unless you are going to get your PhD to do a lot of witting on design perhaps?