I continue to be surprised at the low percentage of graded books at most smallish to mid-sized shows. The thousands of slabs that are for sale on ebay any given week always give me the impression that the market for slabs is far larger. But I still routinely hear dealers explaining to prospective buyers terms like CGC, slabbing, resto checks, etc.
So yeah, there is a big percentage of the hobby that has never got on the carousel.
Look at the cost of getting a Bronze Age or earlier graded - $25 give or take after discount, including sh/ins, etc. I suspect the vast majority of books at most shows are worth $50 or less, so slabbing these books doesn't make financial sense. As such, I imagine the vast majority of books in this hobby are not affected by CGC, slabbing, or pressing. Likewise, I suspect the vast majority of money made by dealers and investors in this hobby is affected by CGC, slabbing, pressing, and this wonderful (d)evolution in our hobby. Follow the $$!
You've brought up another point here. Not everyone is in it for the money. Sometimes people get books graded because it's something they just want a graded copy of in their collection. I collect foreign editions, most of which aren't very expensive, and in addition to that I'm a SS collector. I've always been into autographs and used to go to cons to get books signed long before CGC ever existed. I drifted into foreign comics because, as a whole, US editions are pretty much readily available. You can get on ebay just about anytime you want and find a copy of whatever you might be looking to buy. With foreign editions it's nowhere near that simple. It can take months and in some cases years to track down a copy of a book you want. So many comic collectors out there have forgotten how much fun you can get from having to actually spend time and effort hunting for a book. The thrill of the chase is what keeps the hobby fun for me. Add to that having a book that you've put that much time into tracking down signed and slabbed for the sole purpose of authentication of the signature creates an extremely scarce if not, in most cases, unique addition to one's collection. Do I care if I ever recover the money I put into my books? Nope. I'm perfectly satisfied knowing that I've assembled a collection that would be difficult at best and probably impossible to duplicate.