There is a saying in the Drupal community, "There is a module for that". There are over 5,000 modules that can be essentially plugged into your website. If you can think it up, most likely someone else has already written a module for it. It is much more efficient for a site builder to use a tested and proven module then to write one from scratch. I know that I would rather spend my time on refining the look and feel of the website than writing a module from scratch.