RavenC once bubbled...
The lift bag can be a inflated and attached to the anchor line for a couple reasons: One to help mark the area, and two to help in lifting the anchor to the surface when the dive is over. There were divers that attached a spool line to the anchor line in order to find their way back. They told me the reason they do this is because they are not very good with navigation and they get lost, but I could see how that could be a good general practice.
I did not have these items. My "regular" buddy had these and always said there is no need for you to have to keep up with them if I have them. Since I always dive with him, with this exception, I didn't need one. I have always intended to buy my own, but sharing worked while I was purchasing the big ticket items. It's kinda like we use my dive flag and marker he doesn't need one if he uses mine. Right? Well, if you depend on someone elses, you will find yourself in need of it. So, I will have my own. R