Because I know what both are capable of and never needed them? It's not that hard to think about. Full time AWD systems may be better in a lot of situations, but what most vehicles call AWD nowadays doesn't help much aside from extreme conditions. You've either put yourself in a situation that requires it or underestimated the weather and need better tires. I don't need first hand experience with AWD or snow tires to say that I've been perfectly confident with RWD and all seasons, both with/without ABS and with/without traction control. Granted I live in an area that only gets 2 feet of snow per year, though it is rural and not salted often. I just find it ridiculous that people think they need or suggest AWD because one time they saw some light snow flurries in late February once two years ago.