Maybe because it is difficult to do so efficiently ? It is hard to get per-file information in git, so you would have to be pretty clever to get it working w.r.

Maybe because it is difficult to do so efficiently ? It is hard to get per-file information in git, so you would have to be pretty clever to get it working w.r.t. history. Other bugtrackers which were based on svn had a lot of issues with git because of this.