I dont know who came up whit the Idear to do it like that first, but as I see it thats just my way of presenting the work to a client.
the benefits for doing it this way
1. you can sell you design for a better price (if people see somthing the like then the price becomes secondery) this ofcourse if you havenīt given them a set price
2. the time issue dont you hade when youmade a site and the client desids to make the logo bigger og change the meny system, this way you go over all aspects before slicing and coding
3. the seem to trust you more if the like your work, so you will have more say so about what will work for them.
just would like to say this is a great board and I like the tone of woice around here.
If anyone like my work and need some help feel free to ask I will do my best

to help
Ole