Why follow the speed limit? Because a difference in a few miles per hour can be the difference between life and death.
Adjust your speed based on weather. Adverse weather impacts safe speed. In bad weather, the necessary stopping distance increases. Rain? Snow? Fog? Leave more space. Drive slower.
On the road, conditions can change quickly. Other drivers are unpredictable. One of the best things you can do to prevent a collision is to keep a safe stopping distance. More stopping distance = more time to react to situations.