Why open interviews at Tuck, UNC, and other?

I am not at all familiar with UNC so I can only comment on Tuck. I am an international applicant and I interviewed on campus in Hanover. While I was there, I met a guy from China who had flown in just to interview too.

I can see your point in that some people that take advantage of an open interview did not stand a chance in the first place. However, for an applicant it's also a huge opportunity. Say you would a borderline candidate. There are no guarantees that you would have been invited to interview. However by showing up and demonstrating your interest and then also doing great in the interview, that might be the extra push you need to go from a ding to WL or WL to admit. Another reason for the open interview for Tuck is that they want to make sure applicants understand the location, the culture, etc. I have heard of applicants who turn up to interview, sit in on a class and realise that the small town, small class size, etc is just not for them. For Tuck, fit is very important.