Security in daily life means to succeed worst case situations
It would be absurd to try to practice the encounters with other dogs, wildlife, joggers and so on. At the most you may be ready to face the events you have practiced for but not the worst-case scenario. Instead you will learn to teach your dog how to react promptly to a signal or call in any unexpected situation. This is by far the more rational approach, and is the only way to ensure the dog and her environment will be completely protected.
Everything else is training your dog for failure.