why implement backwards design?

This post from the i-clicker blog discusses backwards design in the development and design of a course. This is very similar to what Team-Based Learning also advocates:

1. Start with the learning objectives. 
2. Design the assessments that will determine whether students meet those learning objectives.
3. Then determine the content and activities that will develop students' abilities to master the learning objectives. 

I still have along way to go in properly implementing this in my existing courses. It's difficult to re-tool courses that are already received well by students. So what propels me to retool them using backwards design, TBL, authentic assessment, or flipped classroom approaches? Even though my students provide feedback indicating that they enjoy my courses and that they think they learn much, I am unconvinced that true learning is happening. I say that because students often forget what they have learned from my classes between one term and the next. I need to change my teaching practice such that the memorize-regurgitate-purge learning cycle is no longer successful in getting students through my courses.