Why is internet restriction software available and important?

Say you had little 8 year old kids that stumbled across porn on an internet website on accident, You would have some explaining to do, Or say you were the owner of a business and your employees didnt do any work all day because they were too busy chatting it up on Facebook all day, you would want something that either reports or/and restricts their movement on the web. Those are just two examples there is many more.