You are thinking about the feelings of the victim. That’s fine, but it’s not the point of a guillotine.

The real purpose is to make the spectacle more gruesome to the spectators. To create fear.

Guillotines were made for political purposes. To eliminate opponents and to tell about it to as many people as possible. When many can watch, then many will know. When some of them can watch closely how the head is separated from the body, and the blood flows, then they will be talking about it. Many times, and for a long time.