The very term "flipped classroom" assumes a baseline model of learning that became ubiquitous only in the last 150 years or so. Assuming the baseline is the "sage on the stage" model where the instructor uses lectures to introduce students to new concepts, the term flipped classroom refers to moving that initial student engagement with new concepts outside of the classroom (to the personal learning space). This transfer then allows the classroom or group learning environment to become "a dynamic, interactive learning environment where the educator guides students as they apply concepts and engage creatively in the subject matter" (https://www.insidehighered.com/digital-learning/article/2017/05/17/author-flipped-learning-discusses-what-it-and-how-professors-can). 

A typical flipped classroom might ask students to view videos on their own and engage in collaborative learning, such as discussions or debates, exercises, or projects in the classroom. 

This model is beneficial for a variety of reasons--it has the potential to more readily surface in the classroom (or online classroom) student struggles with concepts or assignments; it levels the playing field for less outspoken or extroverted students, since they can often engage 1:1 with an instructor rather than speaking in front of the class; and it brings into the group learning environment higher-level learning, moving initial understanding and comprehension to the personal learning environment. The benefits of presenting new concepts via video, one outlet said, are "counter-intuitive" in that they are human: one proponent commented, "“I now have time to work individually with students. I talk to every student in every classroom every day" (http://educationnext.org/the-flipped-classroom/). 

Working in courseware development for higher education, I've seen that professors/instructors are wary of and resistant to this concept. Why is that? There is some generalized fatigue toward what educators see as trendy ideas or buzzwords--the flipped classroom has been encouraged by policymakers and discussed by technology providers, which sometimes spurs reactionary feelings in faculties. Anecdotally, I've also heard from educators that students often see in-person lecturing as what they are paying for--they might not see instructors engaging individually with students as "teaching"--this effects those all-important course evaluations. 

Robert Talbert, the author of Flipped Learning: A Guide for HIgher Education Faculty, has some additional ideas (backed up by data!) about that (https://www.insidehighered.com/digital-learning/article/2017/05/17/author-flipped-learning-discusses-what-it-and-how-professors-can). The rewards system in higher ed is so often to blame for conservative trends in these settings--changing a course or model means experimenting, which can be risky and challenging in departments that grade instructors on student evaluations and often do not focus on achievement in the area of student learning (instead encouraging professors to research and publish in their discipline). More surprisingly, perhaps, his research also indicated that instructors were more likely to experiment with flipped learning if they had a personal relationship with a colleague who had flipped her classroom--this was more likely to sway them toward this than efficacy research, for example. 

While the flipped classroom is enabled by the ease of recording lectures, aspects of it have long been in practice: think discussion groups and labs recently and further in the past the dialectic model of learning. Technology here allows for efficiency but has not created this innovation. 

http://educationnext.org/the-flipped-classroom/

https://www.insidehighered.com/digital-learning/article/2017/05/17/author-flipped-learning-discusses-what-it-and-how-professors-can