Why does our society place more value on the degree than the actual learning?
I agree that there is some utility in this way of thinking about formal education, but I also think that this perspective is so shallow that individuals who learn to adopt a richer perspective may learn more and may be able to do more with their learning.
First, I think it can be useful to reflect on the benefits of learning that have nothing to do with social status or employability. Is there intrinsic value in learning and in learning how to learn? Does a high-quality learning make one a better person in addition to increasing social status and employability? Understanding those benefits may improve motivation to work hard and effectively as a learner.
Second, I think it can also be useful to reflect on a more sophisticated manner on the instrumental value of education: those who view a degree program simply as a means to a credential fail to internalize a narrative of self-development and growth (self-consciously directing one's education to increase skills, insight, and wisdom, for example), and as an educator I've found that those of my students who grasp on to such a narrative learn more and learn better. Higher education institutions gesture towards this idea with statements about fostering lifelong learning, but those statements tend to be empty platitudes without corresponding curricular or co-curricular content.
So, one reason why society places more value on credentials than on the learning that underlies them is that too many learners fail to question a shallow and limited viewpoint on the purpose, nature, and benefits of education. Individuals can benefit from rejecting that perspective, and institutions of higher learning have opportunities to help their students do that. Hiring managers may always value credentials highly because they don't have the ability to assess individual learning, but learners and institutions of higher learning can certainly do more to increase the value of those credentials by valuing learning more highly.