[biot]

  > A great designer can change the UI elements on a Photoshop
  > document in about an hour.

If you had an artist paint the UI mockup on canvas, it would take longer and cost even more! My point is why is Photoshop still used as the default tool in many places? Photoshop is meant for photographs. We have so many tools at our disposal which can give lightning quick feedback: change a single CSS element from "color: red" to "color: green" and the entire site updates as soon as you save the .css file.

Why, then, do people still use the digital equivalent of painting on canvas? An effective design agency would come up with the overall information architecture including layout, font, and recommend color scheme based on the client's brand. Then give the client a very user-friendly tool to adjust the elements that the designers have specified as being configurable. The design agency can put whatever constraints on it they want, but then let the client have at it while the designers guide the client through the whole design process, offering feedback on why something does or does not work.

[hcarvalhoalves]

> Why, then, do people still use the digital equivalent of painting on canvas?

Because anyone who pilots Photoshop can use the title "web designer" and still get hired. It's somehow accepted by most in the industry that the work of a designer stops at a mockup.

> An effective design agency would come up with the overall information architecture including layout, font, and recommend color scheme based on the client's brand.

This is what designers are supposed to deliver. In the real world, the managers will ask for a mockup of the product, something they can show to stakeholders right now to show progress, and that will almost never be implemented because requirement changes/flaws will be found during development, and the design ends up being realized by the developer. I've worked on / know about a handful of companies where the process is exactly this.