Most of the examples here will be in context of Grixis Deaths Shadow, half because that deck plays both of these types of cards and half because that deck is still insane
Myr are not exactly a powerful tribe
As a result, it's only targeting one opponent, and Zevlor will copy the spell and give you both effects for each opponent you currently have
Liliana the Last Hope makes your edict effects a bit better and is great against the Tribal decks and against Delver
Early sets included a few cards with rules designed to interact with this gambling aspect, allowing replacements of cards up for ante, adding more cards to the ante, or even permanently trading ownership of cards in play
The fact that these at least give you a reason to enchant your opponents creatures would eventually open up a new possible deck archetype, which is great for the card type