There are good reasons to have a Child theme:
- Theme Updates: If you make changes to your theme programming code and later update the theme, all your changes are lost! The child theme lets you update the parent theme and keep all those changes, thus any css styling, security or functionality changes will still be included in your main site!
- Site Development: Having a child theme can really help you speed up the development process. If you are a beginner to developing Wordpress themes having a child theme lets you tinker away without causing a major problem to your site. If you make a mistake you can just undo the changes in the child theme and the parent theme will take over the original operation.