I've been on a few interview panels recruiting for my agency's grad program, and I can think of several times where we ended up rating a candidate with strong academic qualifications below somebody who might have appeared "weaker" on paper.
Some areas where the academic high-flyers may have difficulty:
Inability to put academic knowledge into practice
Somebody I knew once asked me for help figuring out the height and width of a display screen that had a 16:9 aspect ratio and a 22-inch diagonal from corner to corner. (Or something of that sort, I don't recall the exact numbers.)
I'm sure that if I'd asked this guy "what is Pythagoras' theorem?" he could have given me a perfect definition. But he hadn't recognised this as a case where he could apply that knowledge. I see this now and again with strong academic performers who haven't spent too much time outside academia.
Inability to tailor communication to the audience
Having knowledge is great, but in the workplace often you need to share that knowledge with others. There's a considerable amount of skill required to do so effectively, and many people with strong academic credentials are terrible at this.
At university you can usually get away with this. Your lecturer already knows the content, so you just have to demonstrate that you also know the content. But in the workplace, it's often necessary to tailor communication to the audience - what does this person need to understand, and how can I bring them to that understanding?
Inability to sustain productive working relationships
A few years back I worked with "Bob". Bob was phenomenally smart, I learned a great deal from him, and he was absolutely driven to get the job done. He built a sophisticated IT system single-handedly. I didn't see his academic grades but I expect they were superlative.
He also had zero tolerance for time "wasted" in meetings, and zero interest in persuading people why he wanted to do things the way he did them... or listening to why they might want him to do them a different way.
So he never talked to our IT team about what their processes or requirements were, and he never got their buy-in for what he was doing. So we ended up with a complex and crucial system that our IT crew hadn't agreed to support, and badly soured relationships between my section and the IT division. After Bob left it took years to mend relationships and some of the old hands still get twitchy when I mention certain software products.
So, yeah, "charm" matters. The wrong kind of charm can be a negative in interviews - I've seen candidates who were obviously trying to hustle me and bluff their way through stuff they didn't know - but people skills are important in even the most technical of jobs.
Inability to deal with uncertainty
University study is something of a controlled environment. When you are given an assignment, the parameters for that assignment will be clearly defined, and once defined you can usually rely on them. If a lecturer were to say "I'm changing the due date from November to October, and Question 3 will now be replaced with something entirely different" after students had been working on that assignment for a month, that would be considered extremely inept; out in the workplace this is just the sort of thing that happens, and we want candidates who can roll with that.
Lack of examples to demonstrate key capabilities
Not every academic high-achiever is weak in these areas! But it's not enough to have these skills; you have to be able to convince the panel that you have them. Academia may not be the best place to collect examples that you can use when the interviewer asks "Tell me about a time when you..."
When I interview, I'm generally rating a candidate in five or six different areas, and they need to convince me that they're at least "suitable" in ALL of them. "Technical skills" is one of those criteria; scoring well in that area is helpful, but on its own it's not nearly enough.