The analogies you have offered aren't great.

For example designers and developers both use the computer as their primary medium of working. Their outputs resemble each other very closely, despite having a different underlying form.

Contrast that to the interior designer building a house, well those are different mediums. There is no efficiency gain from the interior designer designing the plan and also implementing it. Where as with a designer working in code there is one.

Fashion designers do indeed make clothing by hand, it's a very important part of their craft. This example disproves your stance.