True, HCL is necessary to break down proteins - though it does not break down proteins itself but rather combines with another item to produce pepsin which begins the process of breaking down proteins in the stomach. Betain helps the body produce HCL. Why it is not deemed necessary by some of the top digestive enzyme makers I do not know, but I am sure there is one or more reasons. Since HCL is a necessary component of breaking down proteins it just amazes me that mainstream products are designed to block HCL production. Most instances of stomach distress such as acid reflux are caused by LACK of HCL.
Here's a pretty good write up on digestion: