The Factory Crimp Die is not necessary. People loaded for years before they were invented. But they sure are nice.
Now, don't confuse "crimp" with "roll-crimp". They are two different things.
To crimp a case is to do something to it to make it grip the bullet tighter. "Roll crimp" is one of three different ways to do this.
Most automatic pistol cartridges use a "taper crimp". The taper crimp is built into the seating die (just as the roll-crimp shoulder is built into the seating die of a revolver set).
This shows a roll-crimp. It's a rifle case, but it works the same with pistol.
This is a reloading die, cut in half. See the two areas that are circled? Notice how they curve inward? When the case is shoved up into the die, the case mouth hits that area (called the "crimping shoulder") and it literally "rolls" the case mouth inward into the bullet.
An auto-pistol case, though, is more like a funnel. The die gets narrower as it goes up, and as the case is raised into the die, it is squeezed inward, so that whole of the case is tapered and holds the bullet.
So the FCD is not necessary. Your 380 dies will load perfectly satisfactory ammo without it.
I just think it's nice. Got one for every cartridge I load, except for the couple of strange ones where they don't make one for it.
Meddle not in the affairs of dragons, for thou art crunchy, and taste good with catsup - George of Lod, Year of Our Lord 297
I always take precautions.
Beware the Evil Bullet Fairies.