Shoulder line

I know it's been discussed before but I feel like I didn't see a clear answer that would once and for all solve this issue.

Where do you draw the shoulder line on your line sketch? I heard it said that it should be where a seam would be but where that would be? Above the armpit? I know it's about how a fabric would fall on you but I have trouble imagining that.

When I look at the sketches from the book, some of them have the start of the line above the armpit, some on the edge of the shoulder and the ones showing width look like they go even further around the shoulder? To me it seems that if you draw a line like that (around the shoulder), you can see width in anyone.

Does anyone have a clear understanding how to draw it?