AndrewJake

I did not interview or have any contact with anyone at Michigan before I was admitted with a fellowship. I didn’t interview at Michigan State before acceptance and I don’t believe they do them, although I’m undergrad there so my situation is different. From what I understand Amherst doesn’t interview and I don’t think Penn does either. At UCSB interviews seem to be sort of a formality. If you’re invited to their weekend I think they have pretty much made up their mind and just want to make sure you fit. I think in general though interviews only happen if a school is strongly considering you. Also, some schools that don’t interview still do English proficiency chats with international students sometimes. 

A sample size of one isn't very helpful, I know, but here is my personal experience with interviews.
Out of four applications, I received one outright rejection, one interview followed by a rejection, and two funded offers with no formal interview. One of the schools where I got an offer never made contact with me outside of my application materials before rendering their decision. At the other one, I had visited my POI (who is also the graduate program director) the previous summer and talked with her about my research and my goals. She mentioned during that chat that they usually do interviews, but that they would not in my case, since she and I had already spoken.
I do think the two contacts I had (one formal interview and one informal chat that ended up serving as an interview) affected the outcome of those two applications. At the formal interview, the questions I asked about the program left me feeling like it wasn't the best choice for me, and I think the committee agreed -- in any case, they didn't accept me. At the informal chat, my POI and I really connected over our research interests, and I'm certain that she advocated for me during the application and funding process.

I have not even gotten a decision...what program?
So it seems like everyone on here is pretty comfortable calling or emailing  the department their applying to  for updates as they wait?  I followed up once last month just to make sure my application was in order and haven't bothered them since.  Of course I want to scratch that itch, but also don't want to be a bother and at this point I can't see how it will have any impact on the outcome.
Good luck to all.