Most zombie decks are fine with self mill and will gladly load up their own graveyards so they can get some sort of benefit, or just set up a big Rise of the Dark Realms to create a huge army
The Treasure token in the Chasing Adventure drop is a ring from the Sonic series, and in these games, the player drops rings when damaged
If you wanted to invent an entire line of Pokmon- ex like thatBulbasaur ex , Ivysaur ex , Venusaur ex then they would need to specifically state Evolves from Bulbasaur ex and Evolves from Ivysaur ex
These reasons include the card's rarity, popularity, age, and design
Now, let's break down the most popular ones
It would be nice to see the mechanic come back in future sets, and if March of the Machine: The Aftermath is any indication, it does seem like jump-start is still on the mind of Magics design team