D&D players often wonder why cone of cold is a fifth level spell, while fireball is third level, when they do equivalent damage over multiple targets. The main advantage of cone of cold is that it’s completely safe to use. A fireball will explode and fill an area, and in a closed room that can just as easily kill you and your friends. If the room is smaller than the area of the fireball, you’ll get fried by the blowback. This is also true of the third level lighting bolt spell — there’s rebound potential if you judge the distance wrong. There are no rebound concerns at all with a cone of cold. It’s a ray of frost that can be shot at someone only 10 feet away, and with a wall behind the target, with no chance of damage being inflicted on the spellcaster.
Also with a cone of cold, you don’t have to worry too much about collateral damage. It’s far less likely than a fireball to destroy things. The saving throw vs. fireball for most items is extremely hard to make (17 for ivory, 18 for jewelry, 25 for scrolls, etc.), which means most items and valuables will be destroyed. Those same saving throws vs. frost tend to be ridiculously low (1 for jewelry, 2 for scrolls, 2 for ivory, etc.). Magic potions are really the only things you have to worry about (which need a 12 to save vs. the 15 for fireball).
Even outdoors there are advantages to using cold. Fireballs and lightning bolts can easily start forest fires, and burn down houses. Sometimes that might be desired, of course, but in most cases probably not.
Basically, cone of cold is a safe spell to use, and I suspect that’s why Gary Gygax made it higher level than fireball, even though the spells are equivalent in terms of the damage they inflict on their targets.