Close neighbor/landlord of mine (since passed) was a water bomber pilot.  He had a few horses and we farmed his acres and supplied him with hay.

About the most mild mannered fellow you could ever meet, always thought most people would think the pilots of those would be some strapping macho combat dude but he was about the polar opposite haha.

The reason they have those planes in this part of Canada is because they are a good fit for our conditions - lots of lakes and rugged terrain that is very difficult to access any way other than by air.  In more arid areas, such as the western USA, water bombers don't make sense as not enough easily scoopable water around. 
They work most efficiently when water is close to the fire, then they can make many drops per hour and get something accomplished.