Social Worker Question:

We all have some preferences. Someone likes vanilla ice cream, while someone else prefers strawberry one. It is the same with people. Some of us like to work with children, while some of us prefer to work with alcoholics. Some individuals with special motivation even choose groups such as drug addicts or homeless people.
Recruiters try to find out why you are interested in specific field of social work. In a good answer, you should simply state that you feel close to the target group or to the job itself. To give a specific reason, such as personal experience, is a great idea too.