Entropy. By adding new features to a system it's complexity can only stay the same or increase. Complexity can only go down if we take time to refactor the code

Entropy. By adding new features to a system it's complexity can only stay the same or increase. Complexity can only go down if we take time to refactor the codebase. Adding new features is cheap and quick, refactoring is usually expensive and slow, hence software entropy, which somewhat relates to quality, usually goes up and up.