Something always bothered me: why using "sketch-like hand-drawn pencil" like style for that kind of tools ? I understand that "wireframing" is some kind of "brainstorming" tool, so it is used with a pencil and a whiteboard in a meeting room and require to draw/erase fast iteratively... so it's the "right" tool for this job... But as soon as you use a computer instead of a pencil, why not have a "realistic" and "clean…
The reason that I've heard used repeatedly is that a shocking percentage of folks who aren't Technology producers can't separate visual quality from "doneness" of a project. If you show some business folks something that looks like it works, they'll mentally update the project to "Nearly done!" and then everything else after that becomes "Unreasonable delays."
If everything is either an obvious sketch, or pixel perfect you can get decent feedback, but a design that is just a little off in jarring ways will distract people from the functionality or design intention.