It may be hard to believe but there are times when an insurance company can be required to provide coverage (to pay benefits) in situations where it never intended to do so. The legal theories that create the obligations have always been confusing and even confused with one another. A blogger has taken the time to post a long article that goes a long way to clarify the situation.
Sometimes when an insurance company does not have an obligation to perform, it can be required to pay anyway. There are typically three doctrinal hooks that force insurers to provide coverage in circumstances where the terms of the contract strictly speaking does not require them to do so: waiver, estoppel, and “mend the hold.”