What am I doing to scare away prospective PhD students? During PhD admissions, our department assigns each admitted PhD student both a faculty and grad student contact, and we make every effort to express our excitement and enthusiasm about the student joining our program; often the faculty contact is a prospective advisor.  Usually there are some nice conversations, which provide a nice prelude to the on-campus visit.

In one or two cases, I've had a student simply stop responding to email.  In this instance, a student I admitted who was initially glad to talk to me quickly cut off contact with both me and the grad student contact (even before the visit).  I am trying to understand if this is a bad sign, or if I'm just reading too much into it.  It's been a long time since I was a PhD student, and I suppose there are a lot of reasons for this behavior.  Still, during my own PhD visits I was sure to be very polite and timely with everyone who contacted me.

Question for current prospective PhD students: Why would you give a faculty member the cold shoulder, rather than just replying politely and briefly to their email?

I can come up with lots of hypotheses (busy with classes, overwhelmed with contacts from faculty, or simply not interested in the program), but all I can do is guess.  I want to hear from the latest generation of students: what makes these interactions with prospective advisors tough?
I am not a prospective PhD student but a current one, and I am not in the mind of every PhD applicant, but my best guess is that some are not really interested in your department, some don't know how to say "I actually accepted an offer at a different school" with good manners, some are not fully sure if the e-mails come from a human or from an automated system (especially those who come from countries with a strong culture of professors ignoring or being mean to students, especially undergraduate - I wouldn't have imagined I'd receive personalized e-mails either!), and some are just rude. Or maybe it's just generational: in the same way it's starting to be considered more polite to never reply a text again than to politely decline a second date, and that many prospective employers say "we'll call you" after a job interview and they never ever call, there might be some perception among some people that it's better to be silent than to reply negatively? I don't know. Do they get interviewed before receiving an admission offer? Are they aware of how many offers you make out of a larger applicant pool? Emphasizing that might entice some of them to continue the conversation, or at least it might dissipate the question on whether they were not aware of things or, instead, they were plainly impolite.