Ok. I live in a small, flat city with few trees. So why did my police department buy these?

Obviously I don't know the specifics of your city, but in general there are a lot of scenarios where it's valuable to get to a scene very quickly (no traffic, etc.) and obtain reconnaissance. Especially violent scenes, or it could even be a drunk driver who is still on the move, or a stolen car where the perpetrators are likely to flee on foot if stopped.

I'm sure you can come up with a lot more ideas using your imagination.

Thanks for the explanation. I will ask my local city council to spend the money elsewhere.

Sounds like a scam

One of the best reasons is that a very large % of calls can be cleared without anyone actually going to the scene. Many cities using drones as first responders now report that they clear ~30% of calls with just a drone. This is great for small cities/towns that struggle to recruit officers and have had ballooning labor costs for police in order to get people to work there. Its also great philosophically if you want police to be involved less, because it dramatically lowers the amount of time they are going to scenes

Can they drive straight to you at 60mph without stopping?

Got it, a surveillance missile.

Common missiles go about 900 mph faster...

There's more than one definition of missile. Florida criminal code's just one place where a drone could be considered a "missile".

Florida criminal code:

  "790.19 Shooting into or throwing deadly missiles into dwellings, public or private buildings, occupied or not occupied; vessels, aircraft, buses, railroad cars, streetcars, or other vehicles.—Whoever, wantonly or maliciously, shoots at, within, or into, or throws any missile or hurls or projects a stone or other hard substance which would produce death or great bodily harm, at, within, or in any public or private building, occupied or unoccupied, or public or private bus or any train, locomotive, railway car, caboose, cable railway car, street railway car, monorail car, or vehicle of any kind which is being used or occupied by any person, or any boat, vessel, ship, or barge lying in or plying the waters of this state, or aircraft flying through the airspace of this state shall be guilty of a felony of the second degree, punishable as provided in s. 775.082, s. 775.083, or s. 775.084."