If you want someone to stop something you have to offer them a world of opportunities to replace it. Because you don't know exactly what will slot into that gap due to lifestyle, financial, personality and social factors.

If you want someone to DO something you just need to show that it COULD fill a gap in some other part of their life. If it's addictive as well then they don't need to experiment for long before it's a solid part of their life.

Getting someone to stop plays off loss aversion and sunk cost.