Just as notes you take for yourself are not the same as an edited manuscript, code you write in the cowboy way is not code that other developers should be expected to easily understand and maintain.
If you're a solo developer writing small applications, this might not be a problem. If you're growing an application and a business this is a very serious concern. As you grow, you need to bring in more developers, but with a cowboy codebase it will be harder and harder to keep everyone productive. Instead of writing new features, they'll spend more and more time just trying to undersand the code, and to fix the inevitable bugs.
Quick fixes are a fact of life though, but use them only until a solid patch can be crafted.
If you're a solo developer writing small applications, this might not be a problem. If you're growing an application and a business this is a very serious concern. As you grow, you need to bring in more developers, but with a cowboy codebase it will be harder and harder to keep everyone productive. Instead of writing new features, they'll spend more and more time just trying to undersand the code, and to fix the inevitable bugs.
Quick fixes are a fact of life though, but use them only until a solid patch can be crafted.