Eventually, this attitude develops software that takes all day to generate erroneous results and nobody really understands the code because it was all added qui

Eventually, this attitude develops software that takes all day to generate erroneous results and nobody really understands the code because it was all added quickly without refactoring. It's the dark side of "Do the Simplest Thing that could Possibly Work" which is probably the most misunderstood practice in XP. At that point, every developer on the team becomes an interchangeable useless warm body and the promotion goes to the "rock star" from outside who comes in and rewrites it or surgically fixes the top performance issues.