Originally Posted by
Abe_Froman
I think the issue you would run into this is incredibly twitchy, dangerous steering.
My bikes have my hands positioned in line with the steering axis. No issues whatsoever because my bars are wide. Lots of input required.
In the never ending search for a more aero position, bars became narrower and narrower over the decades. That made steering twitchy as hell. In order to "Fix" the problem stems were lengthened to add the increased sweep that you accurately describe. Then the new problem was a too long top tube, which was easily fixed. So actually the long stem and short top tubes are two "Wrongs" that put a band-aid on the issue, not remedy it.
On a motorcycle, there is significant inertia and centripetal force to overcome just to get the front wheel to turn. This is not really present in any serious degree on a bicycle.
This is not true on high performance motorcycles. The rake, offset, and trail geometry is so twitchy it can violently rip the bars from a riders grip. That's why we see very stiff (or progressive) hydraulic steering dampers on sport and race bikes.
