At one time we had six of these little beauties peeping over the fence at the bottom of our garden, and just out of curiosity my husband asked them exactly the same question. The answer was - Hot Dog Vans!
Our local ice-cream van calls every day during the spring and summer months, then drops down to 2 or 3 days in the cold weather - the ice-cream man makes all his money in the summer then plays golf when it's colder, leaving the van parked in its garage.
Our ice cream van comes around every single day at around 7pm almost every day of the year, including winter when it is dark and the rain is lashing down!