Talking about a site is one thing, but actually framing it out on a page allows designers to discover possible design setbacks before it’s too late.  I’d rather encounter these difficulties on the drawing board.  At least there it’s much easier to correct a problem.

Also, things needed for a website to function properly are sometimes forgotten about on a first draft.  For example, every site should have footer, but was one included for navigation purposes?  Oops.

Or perhaps that interactive flash site is a good idea for most people, but what about the visitors who have Flash (or JavaScript) disabled on their browsers?  Or better yet what about the small percentage of people who still cling to their dialup access?  These folks need an HTML version of your site.  As do the major search engines.  They need actual content to search.  Looks like it’s time to go back to the drawing board!

These are just a few of the reasons why I create interactive mockups.  I get to have fun creating and visualizing a site.  I also get to discover problems early in the design process.  Finally, the client gets to “see it” before he/she buys it.