Binders are a logistical nightmare for anyone in a customer service role.
Years ago I worked for a company that distributed some materials in that manner. On a daily basis we would get calls from people who had their binder right in front of them, trying to argue a point. They would say "I'm looking right here at page ____ and it says ____." Invariably it comes down to pages being out of date. You have to start asking about the revision dates on the pages they are reading and then gently convince the caller that replacement pages were sent out, but apparently didn't make it into their binder. Of course, most callers claim they never received the pages which could turn into a liability for us (insurance industry.)
In nearly every case additional replacement pages were sent and it turned into a vicious cycle.
It wasn't any cheaper, either. I don't know about printing costs today but 10-15 years ago, printing a handful of pages and having them 3-hole punched and shrink-wrapped (which you have to do in order to make sure everyone all of the required pages) was not a cheap process.
From a psychological standpoint, replacement pages also highlight the changes which have occurred. Those who actually do get the pages and go to replace them will typically scour both documents to discover what has changed. That leads to more phone calls and comments from people who just want to share their $.02.
On the surface it may sound like a more honest and up-front approach to take. But my experience is that it generates a lot of negative emotions from customers, often on topics which don't even impact them.