The problem is those shoddy foundations can support a lot of weight before they finally fail. A prototype you write in a day - not a big deal to throw away. However if you have been working for a while that is a lot of effort/money.

Worse, often you need to spend years before you realize how an initial design decision was a mistake - not only are you proposing to throw away millions of dollars worth of work - you also don't know that your proposed better design is really better.