Because sometimes youre just like, Nope, be a bird now. Now you too can pretend to be an insufferable genius from an anime and pretend to predict your opponents every move
You dont try and shoot down every big play as it happens, you have to smother them and freeze them before they ever get off the ground
If an opponent tries to copy anything else, they will have a rules infraction against them, letting you take a point
Resilient, interactive gameplay that scales naturally over time
Since then, things have gotten better for the mechanic, and a lot more varied and versatile Pendulum cards have been released, but I suspect that very few decks outside of Arc-V (and a few Challenges) use them, precisely due to the archetype limitations baked into several of them