Side loading pockets reduce the chance of cards slipping out during travel, while zipper binders add another layer of security
When either of those conditions are not met, the card doesn't get played, or doesn't get played successfully
In Zendikar Rising they were all lands on at least one side, while in Kaldheim they were used for the legendary creature Gods on one side and a different kind of permanent related to them on the other
The more I play with the cards involved the more it is clear how seamlessly you can transition from one iteration of this kind of deck into others and from the broad group of "Blood Artistry" decks into red and white aggro decks, you can even morph a build into a tribal build
Some noncreature spells that greatly benefit from shapeshifters are cards like Harmonized Crescendo, The Bears of Littjara, and Peer Pressure
You can suspend it for with X time counters and when you remove a time counter from it, you'll draw a card