I take people flying, and when they have the controls they tend to put us in a slight bank to the right. This has been happening for years, and lately is starting to bug me. I have a few hours in the right seat, and didn't notice anything obvious, but that was after many hours of instruction. Out of the people I've flown with that are willing to take the controls, this accounts for more than half of them. Always to the right a few degrees. Today was a friends 4th hour and 2nd flight and despite my best efforts could not get him to keep us on a heading. I explained the pick a point on the horizon and keep us going there, let the airplane do the work. Light touch on the controls, and everything else I've been taught. Is this typical or coincidence?