<p>Part of it depends on the size of the program. When I finished my bachelors in a small program, the faculty told me to go somewhere else for my masters because I needed to learn from new professors, and because I had already taken many of their grad courses as an undergrad. I was really ready to move to a larger city anyway.</p>
<p>If someone has an employed spouse and other obligations, then it is more understandable to want to stay at the same college for all your degrees.</p>