As has been pointed out, this could be down to your selection of schools; the range of interviewed:admit on a per-school basis is pretty large.
If there's any chance that you're a poor interviewer, I highly recommend the practice interview, even if you have to organize it yourself.
I've found the single most useful tool in diagnosing problems in public speaking is to videotape the session. I've been through a public speaking course where your sessions were videotaped and critiqued, and believe me, most everyone had some tics or other tendencies that were blush-worthy. And if you told that person the same thing, they'd dismiss it - you *have* to see it/hear it for yourself.
I've interviewed people for employment, and many had nervous habits that were distracting or worse, often ruining their chances for employment. And I'm sure they weren't aware of them, or didn't think I was. Nervous habits like constantly scratching a body part or their hair, or covering their face or mouth with their hand, constant sniffing, mumbling and/or an inability to make eye contact, poor posture, rocking behavior, etc, as well as inappropriate emotional responses, comments, or familiarity, all these little things turned "great prospects", based on their resumes, into "unsuccessful applicants."
And, like I said, most people, if you told them "Hey, you scratched your scalp so many times, it looked like you had lice" would dismiss that as an exaggeration. But the tape doesn't lie ...
So, do practice sessions, even if you have to organize them yourself, tape them, and review them.