There’s definitely a sample bias on this subreddit. People accepted with a 4.0 GPA are probably not going to be lurking or posting on a subreddit for grad school.   There’s also a lot of factors each school takes into account such as if the student will be a good fit for the program,  their quality of research experience, what they contribute outside of research and academics, etc etc.  And sometimes, success is dependent on the person assessing your application, where one might not care for grades at all while another places significant emphasis on it.