I had to do some research on fire fighting for a novel I was writing in which the main character was a firefighter. The amount of equipment they have to use is amazing. Not only do they carry huge amounts on their own bodies, they also have to learn how to use all the things they have on the truck.
Apparently there are only a couple of companies in the whole United States that even make fire truck equipment now. They have to be very careful, of course, because reliability is so important.
And the trucks are so expensive that they can only really afford to replace them every few decades. Which is why you don't often hear about old fire trucks for sale.