I accept that legal case, but if there is no claim and it wasn't my fault then why the penalty?
For insurance purposes the 'fault' is either 100%-0%, 50%-50%, or 0%-100%.
In reality the 'fault' in vast majority of accidents is actually more like 80%-20%, or 60%-40%, etc.
In other words, a good driver will avoid most (though not all) accidents, 'at-fault' or otherwise.
As an example, you crash into someone at a junction, you had a green light, his was red. Could you have avoided the accident? Probably, by applying better observation even though you were entering the junction at a green light.
The insurers consider careful drives who avoid all accidents to be a lower risk overall than those drives who are not as good or mindful and tend to have 'no fault' accidents.
Statistically, a driver that is involved in a large number of 'no-fault' accidents is more likely to be eventually involved in an 'at-fault' accident - hence why that driver is a higher risk and will pay a higher premium.