Aging is bad because it hurts quality of life. Right now, people live longer than their bodies can perform at full capacity. Most people would prefer to remain healthy for their entire lives. No matter how ready someone is to die, no one wants to spend ten years in a nursing home. So everyone could find a way to die before then, or they could find a way to stay healthy even if that doesn't increase their life expectancy. You can guess which option is more likely to catch on.

The argument over whether we should fight aging is one worth having, but only as a philosophical exploration. The reality is that we always have fought aging, and we always will, because those who think otherwise have a tendency to die first.