In my experience, the "later" may come too late. I've seen code copy-pasted and slightly modified over a dozen times, sometimes without even eliminating dead c

In my experience, the "later" may come too late. I've seen code copy-pasted and slightly modified over a dozen times, sometimes without even eliminating dead code! Copying a function or even a whole file is fine if you actually take a moment to consider whether it needs refactoring or not, but more often than not people will just copy and bash at the code until things work without actually making a conscious choice to duplicate code over refactoring.