[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.