I would think that it is tradition. Ice Cream or soda for the whole department is standard at our house if you make the news, print or TV, unless your the designated incident PIO.
What is expensive is if you have a call to your house, then you owe then entire department and their spouses a steak dinner on the town! There was one FF on our dept that had happening at home not all that long ago, that individual turned the receipt into their homeowners insurance which unbelievably enough they actually paid; dinner for 60+ and was not cheap I'm sure.