The card could be there because it was milled or discarded, for example
Nowadays, it's a conscious choice (unless youre an indie game dev on a shoestring budget, in which case you're still in the early 90s)
25% of the time, instead of an ad or token card, Set Boosters contain a card from The Listinteresting cards from anywhere in Magics history, printed as they appeared (including art, frame, and expansion symbol) plus a small Planeswalker symbol in their lower-left corner
In the not-so-distant past, Wizards of the Coast implemented Bonus Sheets as a way to both amp up the excitement for new sets, and reprint some much-needed cards into the MTG ecosystem
6: Nova Hellkite This one could make waves in Standard especially if the format slows down a bit post-ban
You may not cast Force of Will from the graveyard for its own alternative cost