Good question, Joey. There are different schools of thought on that. For example, snooker players like to have anchor points where the cue is guided by it's contact with the body --- The theory being that the body actually helps keep the cue traveling in a straight line. Placement of the feet is key in setting up this type of stance.
Other players prefer to have their cue completely free from contact with their torso, and will adopt a stance that accommodates a free-moving cue.
Problems occur when contact with the body is unintended, or when the stroke is inhibited due to a poor stance.
This is why I don't agree with people who continue to say that all you need to do is to stand comfortably. I'm sure that there are a lot of positions that feel 'comfortable' to players, and possibly 90 percent of those positions are preventing their improvement.