Advantages of Black-box Testing
The test team needs no knowledge of implementation issues, including programming languages or other tools used in the implementation of the component under test. This means that it is possible for project leaders to hire non-software people to work out test suites as soon as specifications have been worked out. The software team itself can then continue working out the implementation of the component. [Source]
No need of any specific programming language knowledge by the tester.
Test cases are designed as soon as the software specifications are complete.
Also see:
Black-box Testing
Exhaustive Testing
Limitations or Disadvantages of Black-box Testing