They dont do anything on their own, but the moment an artifact, land, or enchantment cares about how many shiny beads are sitting on it, charge counters quietly run the show
There might be some combat-focused blue deck Im missing
Wilds of Eldraine even features a card with a similar ability - Callous Sell-Sword, which lets a creature deal damage equal to its power to any target in exchange for its sacrifice
And theres collectability, especially when it comes to The Reserved List
Creature Sarulfs Packmate is great at drawing you an extra card that you can potentially play right away thanks to the cheap Foretell casting cost of two mana
Just gaining life twice before an attack makes this a 4 power hitter, which is really good in the limited environment, especially if gaining life pads your ability to take a hit in response