Chances are you will end up downloading a lot of dependencies anyways, why not have git deliver it all?
It could be several orders of magnitude larger and with a larger organization could be a lot of unnecessary code that any given Dev may never touch.
We keep pruning and gc'ing with different flags, but pulls just seem far slower than other smaller repos.
B: Developer working on daily basis in component A finds a bug in component B. He just has to change the code and commit it for review, instead of understanding the specifics of working with component B repository.