For instance, if I have a 3/3 creature, I can put as many +1/+1 counters on it as I want (although once its power is equal to the opponent's life total, the value gained drops off quickly)
You get an extra card in exile to play each turn, while opponents lose their first draw and must play from exile instead
Plus, if we're willing to expand our perspective, we can consider that pulling a land out of our deck is the same as drawing a land, which also makes one less land we'll draw in future draw steps
Keeping cards in good condition isnt just important for those who like to play around with the secondary market, but also people who just want their cardboard to last
You can notably use its second ability on Sazh itself, so it can attack as a 5/5 at minimum and potentially even more if you have other ways to place +1/+1 counters on it
And yes, once again, real bargain-hunters can instead go for the $11 old-bordered version itll go very nicely with your copies of Brain Freeze and Grindstone, which have never been printed in normal new borders