By asking this question, the interviewer is determining your knowledge about automated testing but also something else. Sometimes there are questions behind the questions that interviewers ask. In this particular case, not only do they want to know why automated testing is recommended, but some of the tools you would use to do this. Make sure you include this in your answer.

"Incorporating automated testing into an agile project will decrease the development cycle and enable you to deliver the product faster. Both Scrum and agile encourage the use of automated testing, which includes both performance and regression testing. Tools you can use to do this include Smartsheet, Kintone, Wrike, and Workfront. There are many more, but these are the most common ones."