[heleph]

I think it's difficult because no one particular change is a problem and in isolation they are mostly completely reasonable. It's the accumulation of these changes that cause the code to rot.

There are a whole heap of "human nature" problems that are the same like getting into debt, being over weight, protecting the environment. The short term pay-off is fairly big, the contribution to the long term problem is very small.

Also the person who is often responsible for making the decision may not be technical, so finds it difficult to imagine the eventual impact. Plus in the fast moving field of software development, they'll be unlikely to even be around when it happens.