This rendered sets useless at higher levels, where higher base gear was more common and generally more useful. Initially, Sets were composed only of normal items. While you will recieve the bonus for each specific rune, you will not be able to make runewords using set items. Placing unwanted pieces in the inventory will not count towards equipping a full set.

Named using the appropriate quest reward.

Unsocketed if the bonus of an insert isn't desirable anymore.

Enhanced with Runes, Gems or Jewels if socket slots are open.

Socketed using the appropriate quest reward or Horadric Cube Recipe.

This means that it is harder to part from specific pieces of the equipment, because the pros and cons of changing gear have to be considered, unlike simply replacing an old helmet with a better new one. You may keep finding better Helmets for your character, but replacing the Set helmet with the newly found one will cause the full set bonus to dissapear. The downside of using complete sets early in the game is the eventual replacement of them. While a Set consists of two to six pieces, it is possible to wear two full sets at once depending on your setup, unleashing even more bonus stats for your character. While lower Sets can be used on different characters with nearly identical results, a Sorceress will never be able to attain the full power of the Immortal King because of class restrictions. There are many different Sets, each tailored for certain level ranges, fighting style and even classes. As you equip two or more pieces of one Set, you will unlock additional qualities that were previously unknown of. Sets were designed with the collectors in mind.

Diablo 2 immortal king set