I care! It is unnecessary complexity, and frankly ugly. If you can avoid repetition, then you should, even if the reason is not obvious.

To give you a concrete example, consider caching (or, equivalently, compiling) web pages. Maybe you have 100 articles, which share a common header and footer. If you make a change to the header, then all 100 articles have to be uncached/rebuilt. Why? Because somebody did not remove the duplication when they had the chance :-)