Refactoring is not explicitly to address requirements, but it is vital for overall health of the system, and to ensure future ability to respond to change.
Thus we need to find the right balance between desirable refactoring and less desirable - experience is the key guide here, and fortunately there are a lot of positive experiences available. Simple guidelines such as not mixing refactoring changes in the same change set as a feature implementation or a bug fix help significantly.
Requirements are vital for effective software development - ensuring that when we climb our ladder we find it is leaning against the right wall! Iterative development helps significantly to address this by ensuring improved feedback. And the other agile processes all help to contribute to this.
By tweaking slightly the traditional SCM principles which are so valuable, and applying agile and lean thinking, we can be even more effective in our SCM.