It's been proven that the safest speed to drive is the speed of traffic.
If everyone is driving slow, it's dangerous to drive significantly faster.
If everyone is driving fast, it's dangerous to drive significantly slower.
Adapting to the flow of traffic is better for safety than blindly following the speed limit.
The speed limit exists because most people want to drive faster and it's supposed to just put a cap on that, however if people are ignoring it you just cause more danger by getting in their way.