Why I don’t stutter with strangers

Why I don’t stutter with strangers So as the title says, I tend to speak kinda fluently when I have convos with people I don’t know ,but stutter more with ,for example my mother. Two weeks ago I went on a date with this guy and tbh I was kinda scared I would be blocking or stuttering, but that didn’t happen. Throughout the entire date I talked a lot and never once I stuttered , this is something that always happens when I talk with people my age ( I’m 24) . This might seem like a good thing but in reality is very frustrating, because how come I can’t speak this fluently also for example during my oral exams or job interviews? Does this happen also to some of you ?