Consider the power source (the camera), Canon had to make a compromise between wifi power/range and battery life. Yeah, sure Canon could make a stronger wifi signal, but then folks would complain about the batteries getting sucked down to nothing to quickly. Of the two, battery life probably is more important for most folks.
No different then today's cell phones (2-3 mile range), and the old bag phones (15+ mile range). The bag phones could power a stronger signal then what today's cell phones can giving it more range.
That is a great perspective, and I realized yesterday that my phone's wifi could be a part of the issue, so ordered a $10 case that extends the phone's wifi signal. My fingers are crossed that it does anything, I would be elated if I could get closer to the reported 100' range out of the 6D.