Ninja Grandmaster Saizo lets players set "Ninjitsu Art" monsters straight from the Deck, which is important for those Trap Cards mentioned above
Add in its Landfall abilities and the Elemental goes wild with Lifegain, mana splashing, and direct damage to each opponent and their planeswalkers
Illustrated by rk post Standard Not Legal Alchemy Not Legal Pioneer Not Legal Historic Not Legal Modern Not Legal Brawl Not Legal Legacy Legal Comp
While not mentioned in the FAQ, another reason is that placing tabs will add extra thickness to the surface, and if you had tabs attached to roughly the same spot on all sleeves, that thickness will add up to form reliefs and damage the cards if the band you use to hold the cards was too tight
[2] You can send 3 "Divine Abyss of the Sacred Beasts" you control to the GY, including this card, then target 1 face-up monster your opponent controls