One of the fundamental goals of most Hose clamps is to ensure a tight seal between the hose and the barb, preventing the working fluid from escaping. To this goal, they are designed to provide even pressure on all sides, with no gaps. An example of this would be wire clamps. An obvious design would seem to be simply having a wire around the hose, one end attached to a nut, and the other end to the screw, and when tightened, pulling the ends of the wire towards each other. However, this will leave a gap where no pressure is applied (underneath the screw), and cause a leak. To combat this, the more complicated and weaker design of having the ends overlap and then be pushed apart from each other is used, as this ensures pressure around the entire circumference of the hose.
To ensure a good seal, the barb must be smooth and free of nicks, scratches, or contamination. Stuck hoses should never be removed by slitting them, as this can leave a scratch on the barb which will cause a leak.
The other goal of a hose clamp is to provide mechanical attachment, to keep the hose from coming off the barb. To do this, they are typically placed behind a raised part of the barb, such that if the clamp does not slide on the hose, the clamp would have to expand to fit over the raised part, thus preventing the hose from being removed.