Test scripts are no different. As testers we generate vast volumes of scripts and need to be able to re-use them. It strikes me as odd therefore, that scripts are so often stored against a project. There may be subdivisions within the project structure for each of the applications being tested, perhaps even a definition of which version the scripts have been written against. Indeed If the testers are a constant from one phase of the project to the next, the scripts are likely to be re-used.
The situation becomes worse where large volumes of external resources are involved. A lack of consistency and knowledge leaving the client organisation becomes an issue and the likelihood of finding a previously written set of scripts lowers dramatically.