It's because if you file with your insurance - they will be sued after by your insurance company. When they win you will get your deductible back anyway. Basically they are just trying to keep this out of court. However - are they doing this for nefarious reasons as in they think they will need to pay a lot more if it goes to court and they think you may be a dummy who will lose themselves in the mess an auto accident becomes or are they just doing it to clear up the court system and handle things amiably. Highly unlikely it's the latter.