Part of the problem is that insurers are in the business of predicting the future, which has gotten very hard recently (global warming, cost shocks).

The other constraint is that, jurisdiction dependent, rate hikes are subject to regulatory approval.

Most importantly, the insurance industry does not make much if any money on underwriting. They make their money on investing the float, which only exists if they sell policies. That’s why insurers for the most part are ok posting slightly negative margins on their underwriting.