In 2016 and '17, Wizards of the Coast was trying to figure out how to execute a new type of counter for Magic: The Gathering.
Aether Revolt was in development in 2016, getting ready for a 2017 release. A concept WotC R&D was experimenting with had to do with permanents and they wanted a way that, when they left the battlefield, they could still do damage from the graveyard. Designer Mark Gottlieb took this problem head-on and came up with something with a little pizzazz: The volatile counter.
Basically it would work like this: When a permanent with a volatile counter on it went into the graveyard, it would deal two damage to the other guy. While it's not exactly a lot, a close game could be decided by a fool-hardy choice to kill something quite easily. Get enough of those cards in the graveyard, and your opponent would be bleeding life.
As Mark Rosewater tells it, volatile counters were initially very popular in playtest and meshed fairly well with the rest of Aether Revolt.
"Volatile counters proved to be very interesting," said Rosewater. "You could put them on your own things to either discourage your opponent from destroying them or to sacrifice them and get in extra damage, or you could put them on your opponent's permanents to either discourage their use or create an extra bonus when you destroyed something. Around this time in design, we were also toying with possibly having some cards with proliferate—and the volatile counters worked nicely in the ecosystem. (Design did also toy around with dropping fabricate, which is why we had two mechanics for a while during design.)"
As the final completion date came close, however, volatile counters proved, well, volatile. Mechanics released in Kaladesh made it difficult to quantify the counter. Not only that, they also proved hard to track due to there being different types of counters throughout the sets. Since the counters were everywhere, players on would totally forget they were, surprising both the player using it and the opponent. Most importantly, volatile counters were seen as "too real world" and not enough of the fantasy-style that MTG is known for. Death having far-reaching and violent consequences could bring down a game fast.
Let's face it, existential dread is not a fun game mechanic.
So, the counters were ultimately nixed before release and a new mechanic was thought up to give Aether Revolt it's own flair. It isn't to say that Magic might not return to this idea in the future - previously dismissed mechanics and counters make it into the game on the second or third try all from time to time, after all.
Just not right now.