Nothing wrong with that... It just likely isn't a good fit.
What does this mean? It sounds like expectations around pay and responsibility. If someone says, "Yes, I'll take your marching orders for 30k per year," why not hire them and let them do that? You might have something with more responsibility open up in the next year or so and have an immediate (and usually harder to find) candidate for that job.
Someone with a mountain of experience coming in has to work against the suspicion that they are taking the role for the wrong reasons, namely that they will bounce as soon as they find something more in line with their actual experience.
It goes beyond expectations of pay and responsibility.
If you take someone with a ton of experience who says they will do the job for $30k/year, their growth expectations are quite likely different than that of a junior person. As such, there's a greater likelihood they will leave sooner if they find something more senior.
And the hard part of this is, they might genuinely be interested in the role. But enough managers get burned by taking in someone with too much experience for a lower level role that leave in under a year, and they tend to avoid that type of candidate.
Now, if I take their low-ball offer, if they pay me as if I had 5 years of experience when I really have 30 and for whatever reason I have to take that job, then yes, I'm out of there as soon as I find someone who will pay me what I'm worth. I like the work, but I do this to make money, not just for entertainment.
And why am I worth more money than someone with 5 years of experience? I don't even work as hard as those people; why am I worth more? Because I get more done, and it's done better when I do it. I don't write the bugs those people write, so I (or somebody else) doesn't have to spend the time finding and fixing them. I don't design the bad architectures that they design. And so on.