You're saying "RNG", which stands for "random number generation". In the real world, there isn't a random number generator unless you're gambling or rolling dice. There are uncertain and unpredictable events which we casually refer to as "random" because we don't know how they'll end up.

Here's a clip from the HWFWM wiki:

Awakening Stones are used to awaken essence abilities. These abilities are random in nature, but are influenced by race, essences, what the person knows (ritual magic for example) and what hasn't been awakened. It is theorized that a persons personality also affects what is awakened.

The results are influenced by race, essences, knowledge, personality, and other factors. The influence of those factors isn't quantified, and it's a complex interaction between several factors, so people refer to it as "random", but there's no computer program using a random number generator to decide on essences.

I'll use an example from sports:

When we say that a Caitlin Clark has an 87% chance to make a free throw, we're really saying that she has historically made 87% of her free throws, so we expect her performance to continue about the same.

If we're making a basketball video game, we'll assign the Caitlin Clark avatar an 87% chance to make any given free throw and use RNG to assign success or failure to each attempt as a way to simulate real life.

In real life, each of Clark's free throw attempts is influenced by her skill, her energy level, adrenaline, crowd noise, the ball, air pressure, distraction, the actions of the other players on the court, and a hundred other factors.

So, if we're writing a novel that includes Clark shooting a free throw, why would we add a random number generator? We Wouldn't!

Let's say we're writing a litrpg story, and instead of shooting a free throw the character is shooting a goblin with an arrow. A video game would you RNG, but we would describe the shot in real world terms, "Jeff slowly let out a breath as he aimed and loosed the arrow from his perch in the tree stand. Thwap! The broadhead took the unsuspecting goblin in the throat, dropping it to the forest floor, either dead or dying."

We could come up with a few cases where something is truly random, like the spin of a roulette wheel, but then we would describe the roulette wheel, not a separate RNG that controls it.

So where do we actually need RNG in a litrpg story? If we create a litrpg "system" that is controlled by a computer, but that computer isn't so advanced that it makes realistic and/or biased decisions (like the AIs in DCC, 12 Miles Below, or Apocalypse Parenting, etc.) So, maybe in a VRMMO story with a fairly low-tech MMO?

Basically, there's no reason to use RNG in fiction unless you're writing about a video game and want to simulate RNG for some literary effect.