Mike,
Honestly, I'm not sure its limited to routing. Does restoring a green show someone how to fit into a site from scratch? Granted, not all renovations are restorations, so more transfers.
Even though few courses are getting built, most of us still see developers bring in concepts. With time on our hands, why not let each associate have a crack at routing? Also granted that never seeing the finished product limits the final stage of the learning process - seeing your mistakes get built.
I was just talking to Derek Duncan the other day. I tend to think a lot of stuff gets forgotten in each new generation of gca's. Just as I have heard young landscape architects take a new tack and suggest Elm Trees, not knowing why they aren't used, I see some young 'uns in gca trying things we tried, not knowing why we don't try them anymore. Even small technical details - like keeping water from flowing into bunkers, onto tees or greens, from above seems forgotten by many. Then they build it and they get washed out bunkers or soggy parts of the tee and green. (Granted, I see some guys are age missing the same fine technical points, too, not just the yutes.
Maybe even more details get lost when things are so busy they get sent out in lieu of the more experienced boss without full training. In reality, most minor construction short cuts don't become evident for a while. There are also a lot of items that got cut from traditional golf course building in the name of cost which really should be there. (stripping topsoil for many builders to save time)
As I get older, it just amazes me that some parts of gca and building just go in circles, and I see similar mistakes to those made 20 years ago, when certain mistakes should have been eliminated long ago via collective experience.