Through testing, it is possible for you to identify complete or partial failures as well as identify bottlenecks in performance that might have slipped during development or in other forms of testing.

Through automation, the predetermined steps involved to run the program can be performed exactly as desired with no interference as well as no extra or erroneous user interactions. This is different from monkey testing as in acceptance testing; only the happy path scenario is to be dealt with.

Testers or any other human resources are expensive than computation cycles. So it is best to automate the repetitive tasks, which will also reduce time that is normally spent in typing, clicking, and digesting the user interface as well by the test user. Furthermore, test can be reused or iterated over, which reduces the amount of tests while making sure that the complete acceptance testing remains while you can focus on other problems.

By keeping a record of various test results, you can gather interesting facts about acceptance testing such as how much of the system under test is covered under acceptance tests as well as how many failures were reported. This can be useful in changing management as well as re-engineering/modernization of the existing software.