Your iPhone has Siri, which unknowingly to you makes your phone constantly vulnerable from various attacks, even when your phone is locked and you sit it down. Anyone can go through your previous messages, make calls, send texts, view your work schedule, add new events to your schedule, FaceTime anyone, etc.
It’s also important to note disabling Siri does not always fix this issue as an older version of Siri is activated, which anyone can use from the lock screen. When we contacted Apple about the disabled Siri issue, they made it clear they see this as a feature.
They also pointed out a well hidden setting to disable the pre-siri voice commands. Here is a video showing some of those vulnerabilities, which Apple considers a feature, which still works in the latest version of iPhone and iPad.