Admission committees want to see that you’ll be able to handle the rigor of medical school coursework. GPA is just one of the metrics they use to assess that. If you were off to a shaky start in undergrad, they’d want to see you were able to recover, learn from your mistakes, and see an improving trend as you progressed through school. If you were off to a great start, they’d like to see you were able to maintain your grades as coursework got more rigorous. All things considered, however, and while they are extremely important, GPA and MCAT will only get you “to” the door. Other metrics such as your volunteer work, leadership, clinical exposure, and other life experiences are what eventually paint an overall picture of you as an applicant, and will help get you “through” the door, hopefully with an interview invite.