It is not that uncommon. Especially with the higher numbers of "qualified candidates." Many times, the interview spots are all filled up and there are many very qualified candidates remaining. Once candidates start doing late season cancellations, spots open up for candidates that were initially waitlisted but may be just as worthy as half of the ones who were asked to interview. Once in the door, each candidate has their chance to impress.
I can honestly say that when I interview candidates, I often finish the day having totally different opinions of candidates than I had when they were just faces on paper. Many times, the ones who knock your socks off on paper are ones that you could not stand to be around for 3-4 years. Similarly, many supposedly average candidates really shine in the personal interviews and the social setting of the dinners, lunch, or tours.
Although scores and grades are important, they are not the only thing to consider and it is unfortuante that many really good candidates don't get as many chances as they should due to arbitrary cutoffs based on scores, grades, and time and money constraints that will not allow us to "just interview everyone."
The main point is to just get your foot in the door. From there, you have a chance.