As time passes, practically no actively maintained codebase is going to clear your bar. It's going to pass through several different teams, with different policies and standards. Eventually, parts of it are going to be put on life support, which generally means an understaffed team that scrambles to patch up the most egregious bugs, often with dirty hacks, because they have no time and resources to do massive rewrites that are necessary to fix things properly. Maintaining such codebases requires a lot of "code archeology", and good history makes it much, much easier.