The difficulty with git in this use case is that it relies on the user to manually commit. If you try the analysis, and decide to throw the code away before you commit, too bad! There's no longer a record of it.
Vizier records everything. Every single change to the notebook, just like track changes in your word processor/spreadsheet of choice. Speaking from experience, it's really nice not to have to think about manually check-pointing... the history is just there.