Even in this age of short development cycles and automated-test-driven development, manual testing contributes vitally to the software development process. Here are a number of good reasons to do manual testing:

• By giving end users repeatable sets of instructions for using prototype software, manual testing allows them to be involved early in each development cycle and draws invaluable feedback from them that can prevent "surprise" application builds that fail to meet real-world usability requirements.
• Manual test scripts gives testers something to use while awaiting the construction and debugging of automated scripts.
• Manual test scripts can be used to provide feedback to development teams in the form of a set of repeatable steps that lead to bugs or usability problems.
• If done thoroughly, manual test scripts can also form the basis for help or tutorial files for the application under test.
• Finally, in a nod toward test-driven development, manual test scripts can be given to the development staff to provide a clear description of the way the application should flow across use cases.

In summary, manual testing fills a gap in the testing repertoire and adds invaluably to the software development process.