I was not thinking of this as a true CAD interface, such as engineers use, but more for people who need a reasonable amount of accuracy but at the same time a drawing that looks good. The looking good part eliminates most CAD programs.
For instance, I'm a landscape designer and I need to be able to draft out a clients landscape plan quickly and easily but then, because the drawing is in part a marketing document, it needs to look terrific. This is where Affinity designer's capabilities really shine. Once the client approves the design it's back to drafting to create more technical drawings like layout plans etc.
I think there is a similar workflow for other professionals who are using Affinity designer to make plans for things that will be created in another medium.
David