If the circle of fifths progression is based on the P5th being the closest partial to the fundamental (besides the octave) it makes sense that we would move in outward expansion from the point of the departure. For example, if a sonata starts in C Major, the second theme would be in G most likely. When this is conduced into smaller terms, the progression I-V7/V-V-I could be seen as an outward expansion of I.
Now here's what I find to be the cool part. What if we go in the opposite direction? Yes, we've all heard a plagal secondary dominant such as a bVII MM7 chord (not that it is not modal mixture). In C, it would look like: I-IV7/IV-IV-I.
If we look at the overtone series in this progression, we might get confused because we as listeners don't automatically assume that the key of the piece we are in is the second partial of the actual key of the piece. That wouldn't make sense as listeners. So what is so awe inspiring about these plagal secondary dominants is that they are an expansion toward Source. The I chord is recontextualized as the V chord. It is as if there is an epiphany or discovery happening, a depth you never knew existed because there was no proof for it in the sonic experience thus far, yet once discovered it changes the perspective of what has harmonically happened. Whereas, an expansion forward in the circle of fifths feels like the creativity of one's self. A metaphor might be. Going forward= the human ability to create from what they have (the fundamental frequency) And going backward is the understanding of what it means to be created. PWAHHH.
My mind is blown and my heart is feeling full. There has always been something attractive about "retrogressions" and perhaps this is why at least I find them attractive and powerful. And this is also just one theory. I'm sure there are plenty more theories that could be postulated. And there are other popular chord progressions that are like phenomenons, well known but not completely understood in conscious or explicable ways.