why's that? i'd actually expect to see something like that for a bunch of reasons...they're known already by the faculty and have an edge over unknown applicants from elsewhere, it's probably easier to get into a fellowship there because programs often take their own (and this goes for residency too) because they know what they can expect from that person (and likewise, the resident knows what to expect from their fellowship program). Also, it's familiar and easier because you don't have to move to a new city, you already know the staff, faculty, other residents, etc. and your friends are there (at least the ones who aren't leaving to do a fellowship elsewhere). simply put, it's an easy and practical way to get a fellowship.