Its a staple in almost every format, and its no different for Old School, where some red decks might need it to win the race
These spells have seen a spike in popularity thanks to cards like Yargle and Multani, but they do well even when youre not starting out with a high-powered creature
When a reanimation-style death trigger ability triggers twice, you cannot reanimate the same creature twice Suppose you have Teysa Karlov and Cavalier of Night on the battlefield, and Fell Stinger in your graveyard, and Cavalier of Night dies
E Wit will grab back the Living Death and we can repeat this process indefinitely for infinite mana
This is mostly to avoid the look of impropriety, as being able to see the back of the card means theres the possibility of marking (i.e., putting marks on certain cards so you can tell when they pop up in your deck without drawing/scrying them)