The question is about why are motorcycles not manufactured with handlebars that can turn to great degrees like a bicycle. In most motorcycles, you hardly have a steering angle of about 20-30 degrees, whereas on a bicycle, you can even go beyond 90 degrees. Is this done with the purpose of stability in mind, as motorcycles travel at far higher speeds than a bicycle, and sudden steering of the vehicle at such speeds can cause it to flip over. Why is this not done at least for motorcycles belonging to the 'streetbike' or 'naked' category, as they are meant to be ridden in cities, at least theoretically, where you might need to take tight turns.
The main reason I have ran into is so that the wider front forks on a motorcycle do not hit the fuel tank which is generally located close to the front forks. Also most motorcycles have a "triple tree" type front end which has to have more frame clearance than the typical bicycle steering stem needs.