So are you asking why hood your bird if the bird is not being stressed by the current situation? The answer is there is no reason, but are you sure what the situation will be in five minutes?
There are many reasons to hood a bird, in my mind the top reason is for the bird's own safety and well being. Raptors are visual animals, so being able to control what they see helps the falconer eliminate any possible negative experiences. Since our ability to understand how a bird interprets what it sees is limited it is better to use caution in new or stressful situations. In any given situation it may not be possible to desensitize a bird, using any of a number of training methods, so the hood is a tool that eliminates the possibility of a negative outcome. Take driving in a vehicle for example, your bird might be fine sitting on perch as you drive down the road, but then what happens if a big truck roars by? Or you get stuck in a traffic jam and suddenly the leisurely drive becomes something else?
The hood is a tool that all birds should be trained to, and used more than people think is necessary.
Paul Domski
New Mexico, USA