@huntducks The binder, depending on the one you choose can either increase the water holding capacity of the meat (Carrot Fiber/Super Bind) increase the amount of protein available for extraction and help keep more water int he meat (Sure Gel, Soy Protein) or all Super Bind does both of those but also forms into a gel around the same temp that meat expells its water.
They will also increase your final yield which is one reason you will find them in almost all commercial products. Yes, the commercial processors are using them tomake them have a better Palate Appeal (Thank you @Joe-Hell ) but they also increase the amount of water that they retain, and water is a heck of a lot cheaper than meat!