It's easy to forget that insurance premiums are ultimately based on opinion... specifically the opinions of the actuaries who analyse vast amounts of data to work out a profitable rate for each risk. Actuaries rarely agree, and that is one of the reasons that no single insurer will ever be the most competitive for all clients in all areas.
The other main reason is that when Insurers change strategy, they don't all do it at the same time. They may price below acturial recommendations for a while to win extra business, but then they will reset their prices to boost profit.
If any Insurer was constantly the most competitive you would expect them to take a disproportionately large market share, but this doesn't happen. |