The intimidate keyword keeps it relevant in combat too
While all great and powerful now, back then Teferi was little more than a strictly better Vodalian Mage in the form of Disruptive Student
There are countless stories of players losing value on their cards by using perfect fit sleeves that were too small and damaged the corners and edges of their cards trying to fit them in
It is the perfect sheen to make any project pop
Decks that are all generally Ancient Tomb + Chalice of the Void decks but are also all trying to cast colored mana spells, in some cases with double pips (in the case of Karn Echo, cards such as Urza, but also any time you ever have to hard cast Echo of Eons which comes up far more often than people might think)
You could buy all 17 for $2,654, giving you every current deck in Standard and still nearly $2,000 left over to buy a Modern deck or two