While I think it's tragic what happened, and the 'right' thing to do would have been to put the fire out once they got there -- since they were called to save a neighbor's house, not the one that was burning -- I don't think they were under any legal obligation to do so.
They offered a pay service to areas that normally would not have any coverage at all. You can get the same sort of deal in many places for trash pickup and municipal water supply. You pay, you get service, you don't pay, they shut you off. This guy knew that and made a choice and took his chances. Yeah, he says he forgot, but I bet he didn't forget his cable tv bill or his drivers license renewal.
He probably didn't have homeowner's insurance either, but I'll bet nobody will get up in arms when they don't replace his destroyed belongings.