Companies not only want to test software adequately, but also as quickly and thoroughly as possible. To accomplish this goal, organizations are turning to automated testing.
To increase the test coverage
Reduces the need for manual testing and discovers defects manual testing cannot expose and also manual testing is error prone and a time consuming process.
Running the tests again and again gives us the confidence that the new work we added to the system did not break the code that used to work and also to make sure that the changes we introduced are working.
Executing the tests (particularly acceptance tests) can also help us understand what portion of the desired functionality has been implemented.