rationale behind git not tracking history of branches

For many years of using Git, I always struggled to make sense of commit history graphs (git log --graph; gitk). Just recently I discovered that git does not track the history of branches to which commits belonged and the lightbulb turned on. This is proving to be painful in a project I inherited with permanent multiple branches. Now, I am a bit curious as to the rationale behind this intentional decision not to track branch history. Is it entirely a matter of keeping branches lightweight?

I am assuming one can backfill for the missing capability by using a commit hook to manually track when a branch head is changed. Perhaps by storing the branch in the commit notes.

Kevin Buchs, Senior Engineer, New Context Services kevin.buchs@newcontext.com 507-251-7463 St. Cloud, MN