Many projects are managed by features. This makes sense as customers pay for and track features, people work on features, features are tested and integrated.
Unfortunately quality is often not considered a feature. Improving the system is frowned upon because it is risky. Work related to features is ok, but work on related to quality is not. Therefor the system does not improve. It may degrade because there is emphasis placed on changes the don't cut across the system and that change the fewest files.
Quality is a feature. Have a quality feature in every release or your system is degrading.