Why is speaking on the phone easier for some, and harder for others?

Why is speaking on the phone easier for some, and harder for others? Some people stutter more on the phone (e.g., bcause their subconscious brain links the phone with [less disruption of executing the speech plan](https://drive.google.com/file/d/1WZxu1N8Ohtv2oPGr857HWt3n6ZHFytdq/view?usp=sharing) \- one example is, that deeply subconsciously the brain relies on the reason that its easier to speak cause the other person isn't judging you as harshly.. as you are not able to see the other person during a phone call). While other people stutter more on the phone (eg cause their mind links the phone call with interrupting the execution of the speech plan more - for example, a reason the brain could rely on is that it links a phone call with the idea that it's harder to speak, or less confidence in one's ability to get the words out, or the idea that listeners are unable to see your facial expressions and thus you need to put MORE effort into speaking, or ANY OTHER IMAGINED REASON that the brain relies on at the moment of speech execution). Some people stutter more if they are angry or scared. While other people stutter less when they are angry or scared. Some people stutter more during loud music, while others stutter less (and more in quiet environments). For example, if the brain links loud music with the need to do more than they are able to, to get their words out or any other reason which links loud music with inhibiting or delaying the execution of the speech plan. Then people may stutter more during loud music. Whereas, other people may stutter less during loud music eg if their brain deeply subconsciously links loud music with the idea that listeners don't pay attention to their speech or stuttering - which could be one reason the brain could rely on during speech execution to link loud music with executing the speech plan resulting in (more) fluency. Conclusion: So whether the stimulus is a phone call, or emotion, or loud music or any other stimuli. The common denominator seems to be that a stimulus is evaluated by the brain at the time of speech execution, and depending on the evaluated value (eg. loud music is linked to speech execution or interrupting speech execution), such stimuli can either increase or decrease stuttering. Even the exact same person, one day loud music (or any other stimuli) can increase their stuttering, while on another day it can decrease their stuttering - when this LINK (between stimulus and outward manifestation) changes from speech execution to disrupting speech plan execution (i.e., the inner judge perceives the same stimulus but evaluates it differently and links the evaluated stimulus to a different behavioral outward manifestation). Can you guys think of other examples?