I have it set up (and many do) so I can highlight a bit of code and see when it was created or touched last, who touched it, and usually what ticket the work was done against -- the context of the change. This gives a whole third dimension of understanding a codebase:

* Dimension 1: Code layout (organization) structure

* Dimension 2: Execution (data-flow) structure

* Dimension 3: Evolution (change over time) structure

All three dimensions try to capture some of the intent of the implementer, and understanding that intent is very important when improving upon the work. Along with that comes a perspective on what assumptions the author had. Code last modified 5 years ago very likely had different assumptions than code written last week -- Being able to see which lines in a function came from which era can illuminate things nicely, and that is only scratching the surface of this evolution-dimension.