Thanks for that Landon, i've never noticed it before but your spot on
Sometimes wobble can be a good thing... R. Crumb used this technique a lot to emphasize how messed up the object was. (I do it sometimes because I need reading glasses and I don't always wear them!) Varying line quality can be a great way to give a stale drawing more personality. Using a brush pen, it is easier to get different thicknesses, and it is more smooth to operate than a technical pen.