When I was younger and even dumber, recovery rides didn't make any sense to me. Every ride was done at 170bpm and just below max effort. Couldn't understand why I never got faster and all my Dutch and Belgian teammates were so much stronger and faster, despite their slacking, drinking booze and living on french fries swimming in gross peanut-butter/mayonnaise sauce for breakfast, lunch, and dinner. Riding slowly seemed a waste of time--what's the point of riding slowly? I can rest on the couch.
It wasn't until I got a power meter and started the Allen/Coggan power-based training regime in the back of their book that I realized how important recovery rides were. Every time you go hard enough long enough, it will affect your spin form. Your muscles get stiff & heavy and don't want to travel in fluid circles. It seems to me that recovery rides are when you focus on and regain that fluidity.
I felt like I was on the right track about this when I saw Froome and Quintana both doing recovery rides on rollers after a hard mountain stage in last year's Tour. Despite living in North San Diego County, I probably ride as many miles on the rollers as I do on the road. And when I get lazy and start skimping on the recovery rides, my HR-to-Watts ratio suffers. What I used to consider a waste of time has become something I really look forward to.