The real use of a safeword
When you don’t have a safeword, when everything you say it’s for real, you can’t shout “no”, “stop” or just scream without actually stopping the fun. Having a safeword allows you to go where otherwise you wouldn’t go. It allows things to happen that otherwise wouldn’t happen.
The most important job of a safeword is not to stop things but to let things happen. It allows the experience to be more cathartic and fun, to be a more full experience.