Examples: Dockside Extortionist, Mana Crypt, Jeweled Lotus, Nadu
That's where Smothering Tithe often comes in, as unless your opponent is willing to spend two mana, you'll be making a Treasure token
If a creature type is new and/or relatively undersupported, but you want to design a card that supports that type
Because the Unknown Event cards are tailored to the specific environment of their respective events, you will see less of them on this list
It seems like every time an enchantment theme is spoiled in an upcoming set, this card gets a boost (dont forget the Gods from Theros are enchantments)
These kinds of deck are less common in the cube than the broad label of "non-agro" and so the vast majority of the best life gain effects are on cards that would still be playable in cube with no life gain at all