Examples of where software might be scrapped and rewritten are:
1. When the cost of maintenance is high and the organisation has decided to invest in new hardware. This will involve significant conversion costs anyway so the opportunity might be taken to rewrite the software.
2. When a business process is changed and new software is required to support the process.
3. When support for the tools and language used to develop the software is unavailable. This is a particular problem with early 4GLs where, in many cases, the vendors are no longer in business.
There are other reasons why software may be scrapped, depending on local circumstances.