The Fragile

Minions popped up in 4th Edition as disposable monsters the PCs can hack through like action heroes. They’re mooks, the disposable thugs villains send wave after wave of at the heroes. Because minions were meant to drop after a single solid hit they have one singular hitpoint. Because giving them 2 or 5 like the weakest monsters in earlier editions might mean a terrible roll or assortment of debuffs would keep a minion alive longer.

This is one of the many ways D&D stopped mathematically representing the world to reflecting the perspective of the PCs. Or, as blogger Wrecan put it, The World is Not Made of Numbers. Obviously, there are not creatures running about that explode if they scratch themselves. They have a single hit point when they confront a hero. In the same sense, there’s no single representation of a creature like an orc or hill giant. If first level heroes stumble through a mountain pass populated by hill giants they might face a single giant that’s a level 3 solo, challenging the entire party. Four levels later they might face two elite level 7 hill giants. And in the epic tier while level 23 the party could face waves of level 21 hill giant minions. The creatures do not change but their representation in the game changes to match the potency of the PCs.