I know it is the opinion of one of the public schools in my home state that everyone is their best self for an interview and most can "put on a show" and the admissions committee feels like because of this it doesn't actually help them make any decisions with admissions because they still just go with the best people on paper as long as they don't royally screw up.
I personally disagree, as it is a good chance to see who is personable enough to be a good therapist + it allows you to show off your program. At the end of the day some students will get accepted into multiple schools and if these programs want our money they also need to tell us why we should want to go to their school. For that reason + others, there is no way I'm attending that school that doesn't hold interviews.
PS I only know this information because my mom was involved in a research study with one of the PTs that is on the board of admissions for that school and she asked him tons of questions.