The simple reason is due to cost. I find many people at trade shows are simply browsing and are not terribly interested in booking anything at that time, if at all. While these books did cost you money at one point, they are now sitting in your home collecting dust and essentially have no worth. Why not re-use them and try to get some value from them?
By giving them out, you are getting them out of your home and into someone’s hand that may not have heard of your direct sales company before. If you try to direct them to your website, they will likely forget and never make it. By having a catalogue, they will idly flip through it while watching TV or something else. If interested, they will contact you to book. But if they do not, you have not wasted more money on buying books that are going to be trashed.
The one problem with this is that they may decide they want something that you can no longer order. One way around this is to only give out books from the last season and which you may still be able to g order from. It is also a good idea to put a expired sticker or draw a line through the front saying this book is expired and some products may not be available any longer. You can purchase these through The Booster or Business Enhancements