I think I did this for one candidate (attending their session after they applied) in the 7 searches I've been involved in. They were already on our short list and did great and so it just confirmed I was already learned reading the paper and the letters.
We have too many applications (800+) and not enough time to consistently do it. Plus, its probably illegal because you do it for some candidates but not for others. That sort of favoritism is a big no no in job searches. So I don't think is common, it certainly isn't for us both because of time constraints and legality.