ICBM does more damage to buildings.
Cost 4 warheads, 1 target.
If you would like to rant about the "unfairness", try using Cruise missiles.
If number of targets are your priority, use CMs, seriously.
They do like 10% of an ICBM damage and only cost 1 warhead.

An ICBM can hit a unlimited amount of targets, as long they are all inside a certain range from the impact center.

A maxed out ICBM has a impact area of 75, so it will hit everything that stands around the province center in a range of 75.

It will also affect every building in a hit city and not split damage in between.

Launch cruise missiles using planes(heavy bombers are my pick)
Because Cruise missiles only have 200 km range, they need to be flown over the target, and then they can fire it

Range can be easily determined by comparing the numbers from other units. If the range is 500, and a cruiser has a range of 100, it’s 5 times farther than the cruiser range.

ICBMs have their perks. For cruise missiles and ballistic missiles, you have to get somewhat close to your target. If they have their country locked down, this can be difficult. With ICBMs you can hit them from very far away, and their massive health can be difficult for TDS to counter. Furthermore, the high dmg means that their city will die if it hits. They are less tactical and more strategic, for when you want to delete a city

if you want to try out missiles, especially CMs, hear my words: max CMs, and use stealth drones. it is just such fun when your enemy sees 5 missiles coming from all directions, directly on their head, without having a clue where they came from. then they think... and send you a message reading 'darn birds... nobody uses them, i didn't think about it'

stealth drone .... after 28 days ... then everything is stealth .... why waste resources and time to make a stealth drone?

Because you don't need a Level 5 Airbase AND a Secret Lab in order to build them, unlike having that requirement for all other Stealth Aircraft.

and, because if you're a drone user, you have been accumulating them throughout the game. and by doing the last research you find yourself with a LOT of visibility (and missile launching ability) inside enemy territory around the globe.

In my personal view, it's the strongest tool in your hands (note the choice of words: tool). But again, 'nobody uses them', which suits me perfectly