I've both had to fight an at fault motorist's insurance on extended rental coverage, and I've also been hand delivered a rental and told to keep it until I'm comfortable with my repaired car by another at fault motorist's insurance.

Ultimately, insurance is in the game of saving money, avoiding court, and reputation damage mitigation. Sometimes you get an insurer that puts their reputation above saving money, but it falls on the claim and the agent to decide how to go about it.