Git tools may be routed in email, but they most certainly aren't used that way by most people. Why would I write a commit message like I'm writing an email if both the commit message and email are the wrong tools for the job? We have issues are PRs for code discussion within the context of code. This priceless information should live with the repo. Not in some isolated silo like email which is not accessible to people who aren't on the chain, or commit messages that are difficult and time consuming to traverse in any but the simplest and smallest repos.