​​Why Cruiser Bikes have high Rake angle and Racing Bikes have low Rake angle?

The caster angle or castor angle is the angular displacement of the steering axis from the vertical axis of a steered wheel in a car, motorcycle, bicycle or other vehicle, measured in the longitudinal direction. It is the angle between the pivot line (in a car an imaginary line that runs through the centre of the upper ball joint to the centre of the lower ball joint) and vertical. 
Rake angle has a crucial role in a motorcycle’s handling characteristics. Generally speaking (means there are exceptions), the greater the rake angle, the more stable the motorcycle is at higher speeds. It is normally accepted that the responsiveness of a motorcycle’s handling is inversely corresponding to the rake angle values. More precisely, the smaller the rake angle, the more agile the bike is. If you take a look at a chopper and a superbike, you will be able to notice the rake difference between the two.
So,if the rake angle or castor angle is high it leads to better straight line stability but cornering capability is reduced.On the other hand.lower castor angle leads to excellent cornering but reduced straight line stability.