I would like you to do this for one of your larger projects at work - just change its name with a simple regex like this - and see how many unit tests fail.

"But I'll just fix those!", you might say, and you might. Except your project is likely not as big as twitter, and fixing every problem is likely to become a much bigger problem.

Plus, you now have to catch all the stuff not caught by unit tests, which also includes design elements that a person has to look at.