Scale of the Wildfire Problem
To the right is a NASA depiction of fires around the globe between September 2003 and March 2004. If we focus on the US to try and understand the scale of the problem, we can use the statistics of fires that spread across 50 thousand acres and more (large fires), in the histogram below. We can also use the statistics of all fires that took place in the US between 2008 and 2018, below (both from the Fire Interagency Fire Center).
Additionally, wildfires around the world are problematic and hard to suppress under extreme conditions. Despite investing vast amount of resources trying to prevent and contain them, experienced personnel and specialized tools can do little to control them with today's technologies. Water dropped onto the flames evaporates and can even drive the combustion further, adding more oxygen to the ignition cycle; chemicals are poisonous to the environment; and both water and chemicals can be hard to drop onto high flames both due to winds that take them away while in the air and due to inability to fly low enough above a raging fire that produces elevated temperatures.