Your son rides his bike without a helmet. Again. You've nagged, begged, pleaded, and informed him of the dangers of riding without one. Next, you've issued Consequences! You've taken the bike away and put it in the garage for a day, then a week and then, a whole month. You've done everything the parenting books say for a consequence to work. It's reasonable. Anyone can live a day without a bike. It's respectful. You're not hitting or calling him names. And it's related. No helmet, no bike. It's simple to understand. But the problem is that he is still riding a bike without a helmet! And the situation could turn into a huge power struggle every time you take the bike away.
Clearly, the Consequence has not worked. Why not?