Not stuttering when reading aloud

Not stuttering when reading aloud I find it quite confusing that whenever I read something out loud, I barely stutter. For example, I play this game with my friends that involves reading something off a playing card and I never stutter whilst doing this, but when we are just having a conversation, I stutter then. Could it be because I have been given something I have to say, without the need of thinking what to say? The science behind stuttering is still up to interpretation, so if you have any other possible theories, please discuss away...