The biggest indicator of success in college is success in high school courses (GPA). Part of that is taking classes that are suited to you so that you can succeed in them. Part of that is putting in the work to succeed. If you can do this in high school, there is a good chance you'll be able to do this in college. Colleges care about their graduation rates, so they want students that will do well. That is why it is the first thing they look at.
AP, etc will tell them your ability to handle harder courses, which matters for more competitive schools.
AP, etc will tell them your ability to handle harder courses, which matters for more competitive schools.