The list of faculty affiliated with a program is a political document more than an accurate document. At my university anyone who is on the faculty and wants to be affiliated with a program may be. Some of the people in the list do not take graduate students. This may be because they are lecturers and do not have labs. It may be that they have retired and yet have not been removed from the list. It may be because they do not have funding. It may be their preference.
My university is not unique in the inaccuracy of this document as a place to look for a potential graduate adviser. I have seldom seen a highly accurate document of this kind. So what is a prospective graduate student to do? You could start with the web pages and publications of the possible adviser. The web pages may also be out of date. They may show a lab of happy people who actually graduated years ago. Dates of publications are a clue.
The lab may still exist and be research productive but not be taking graduate students. You just can’t really tell what is going on from our pages unless you read them very carefully. I’m sorry this is the case, but there is really no other way to have it. Everyone is busy, so it is up to the individual professor to keep their information accurate. Deleting web pages or acknowledging the waning of a career is hard.
So do your homework on the lab group. The only real way to find out what is going on is to talk to a current graduate student in the laboratory. If there are not any, don’t choose that lab, unless it is an assistant professor in the first few years of her career, or is in a small program where everyone doesn’t have grad students, or a medical program mostly run on postdocs and technicians. If you are determined to choose a lab with no graduate students, talk to the professor and ask for the names of former grad students, or of students who have rotated through. I do not want your brilliant career to falter because you were fooled by our web pages.