Every engineer has a different expectation of code quality, future functionality and abstractions to be implemented today.
Code merging and deployment becomes more predictable, engineers know what to expect from each other, rework and refactor ratio drops.
Every onboarding engineer has the same questions, why this, why that, and their first real impactful code push doesn't come until weeks later.
Time to first impactful code push drops to days, hours. Thoughtful questions arise early from new onboarding engineers, not the same patterns again and again.
Fixing one bug in one place breaks multiple others or just simply doesn't fix everywhere, your code became a spaghetti with higher maintenance costs.
Fixes applied are permanently fixing the targeted problem at first try.