All the usual health and family related reasons - tho' had been ignoring these since I started. My reasoning was (and still is) it's my body and I can do what I like with it.
Knowing how the tobacco industry pollutes and exploits people in developing countries. The environmental impact of growing, shipping and processing tobacco. The final straw was indirectly the smoking ban. The thought of sanctioning those energy wasting eco-vandal patio heaters they're installing for smokers everywhere.
Seems smoking brought out my inner hippy.