When design leaders go straight to wireframes or high-fidelity mockups, they define too much detail too early. This leaves designers no room for creativity. One friend put it this way:

I’ll give a wireframe to my designer, and then I’m saying to her: “I know you’re looking at this, but that’s not what I want you to design. I want you to re-think it!” It’s hard to do that when you’re giving them this concrete thing.Wireframes are too concrete

I'll do a separate post on my thoughts on wireframes later on but this pretty much sums up how I feel.