I think the reason might be a little bit more complex than just whether they have a PhD or not.
Maybe it would make more sense when you consider the person as being 'overqualified', moreso than less hire-able?
Let's say I'm some web startup that focuses on making the best todo list app that has ever been made -- If I get a guy out of college who has little to no experience (but the experience is on the stack that I am using), and I have a PhD with a some specialization like robotics or DSP (vague but bear with me), it might not seem to make as much sense (even given that they have the same experience on the stack that my company uses) to hire the PhD with the robotics/DSP, as he it seems that he is a molded part (specialization), that does NOT go into the hole I'm trying to put him in, whereas the new grad appears to be more pliable (if not incomplete), and will definitely fit, and I can try and build up to expand to fill the role.
Don't know if that analogy made sense, but essentially I mean to say that someone with a PhD might be just as hirable, but from a hiring manager's perspective, hexagon block in a square hole (as opposed to putting a circle block in that square hole)
Maybe it would make more sense when you consider the person as being 'overqualified', moreso than less hire-able?
Let's say I'm some web startup that focuses on making the best todo list app that has ever been made -- If I get a guy out of college who has little to no experience (but the experience is on the stack that I am using), and I have a PhD with a some specialization like robotics or DSP (vague but bear with me), it might not seem to make as much sense (even given that they have the same experience on the stack that my company uses) to hire the PhD with the robotics/DSP, as he it seems that he is a molded part (specialization), that does NOT go into the hole I'm trying to put him in, whereas the new grad appears to be more pliable (if not incomplete), and will definitely fit, and I can try and build up to expand to fill the role.
Don't know if that analogy made sense, but essentially I mean to say that someone with a PhD might be just as hirable, but from a hiring manager's perspective, hexagon block in a square hole (as opposed to putting a circle block in that square hole)