Morph isnt particularly strong and doesnt quest for much, but it's cheap, only costing two ink, and since it can come down early, you can set up some great shift plays just a few turns later
Moreover, we've got a good selection of reanimation spells, from Living DeathLiving Death (155,419 decks) to the lowly ReanimateReanimate (484,613 decks)
You get value regardless of what happens to Mulldrifter afterward
We get two benefits here (and again, this is a tendency and wont be true for every individual card): cheaper and more available versions for the players who want them while protecting the investments of the collectors
Fate Unraveler, Underworld Dreams, Razorkin Needlehead, and Kederekt Parasite are all very similar, and theyre often seen in the same decks together