So many comments in the vein of "who has time to waste on candidates we aren't going to make an offer to?" - You are damaging your companies brand thinking this way. You want people who you reject to say to themselves "I can't wait to study up and interview here again, they said no, but I still want to work here!"
95% of the time, you didn't give as strong answers as other candidates. The other 5% of the time, you came across as a jerk.