Not to mention the wind.

Just Google pressure drop in hose. Lots of online calculators. It's hard to push water a long way through a small tube.

The first drone I looked up has a 50 minute flight time with 100kg payload. One drone will deliver more water per minute than a flying hose.

I will look that up. However, the precision from a hose seems better than a bucket.

Nobody said anything about a bucket. Onboard pump and nozzle, IR camera and some software and you can probably get them self aiming. Farmers are already using drones with herbicide and flamethrowers to control weeds. There are also firefighting drones on the market that use dry powder extinguishers for highrise fires. I guess the point is, if you can use the drones to carry a hose, control wires, and water, or just water, then you get more volume out of just water without the problem of pressure drop in the hose. The pressure required goes up exponentially with the flow rate, so it is a real problem to get a decent flow rate unless you increase bore size.
As for precision with a mile long hose, if you can keep the end of the hose within a 10m radius of the target on anything but a completely still day I'll be impressed. The sail area will be massive.