Your still not going to code a WPF form ( or at least I havent been able to) without going into the XAML file. Once you get there you have a whole markup mata data language to deal with. limited IDE support. All to do the same job that I'd do in a winform without it.
That takes time. Thats more code. thatsmore to debug. And in a line of business application thats not acceptable. If its going to take longer and be harder to debug then thier has to be a some benefit.