Why use a page layout program, such as InDesign, instead of Word? The payoff is power. The price is ease of use.
InDesign gives you complete freedom in how you can combine words, pictures and graphic elements. You can vary your design from page to page. You can have multiple flows of text running side by side. There are also tools to help you place and manage large numbers of graphics, and to keep track of changes to these graphics during production. Word is designed to work with a single flow of text and images and a single page layout, and offers only crude tools to manage graphics. If you're not a designer by background or training, Word is much easier to learn. But if you are looking to create a feature-rich, complex graphic document such as a catalog, magazine, manual or promotional brochure, you need the power that a page layout program offers.