Some may wonder nowadays about the importance of lo-fi (low-Fidelity) UI Prototypes.
Even today, when there are many tools to help us design Web Pages / UI with relative ease, lo-fi UI prototypes are still very important due to reasons that may not be 100% clear at first sight.
While it might seem a waste to make a first UI Prototype to "throw away", like what is constantly suggested by UI gurus, here are some key reasons not to stop using lo-fi (pen and paper prototypes being the most common examples) prototypes.
While it may be obvious to many, it's just less risky to create a lo-fi model because when (not if) you have to change it, there's less rework involved.
Users feel intimidated when they look at a prototype that's too detailed. If they look at a HTML/CSS UI, for instance (even if the designer created that particular design in under 3 minutes in Dreamweaver), it will look too daunting for them. They will look at it and think "I don't really like the design, but the designer must have have spent so much time on it I can't say that...". That's the gist of it.