Bob or Sylvan Library or pretty much any other card is better. At least you get value for the card slot and life spent. Or play Spell Pierce/Stubborn Denials.
Street Wraith is bad. You think you're playing with a 56-card deck, but it ends up leading to tough mulligan decisions and awkward topdecks when your life total is pressured but you don't have/need Death's Shadow.
Gitaxian Probe was good because:
-It was a sorcery for Delver, Snapcaster, YP, Storm, etc.
-It gave you perfect information to sequence your next turns
-You could choose to pay mana for it when your life total is pressured
Street Wraith does none of those things. It just cycles for 2 life.
You don't need to aggressively suicide your life total against fair decks. They'll deal you damage on their own. You already have fetches, shocks, and Thoughtseize to help you get down. I could see an argument for it in a heavy combo meta where you just need to be explosive as fast as possible. But this meta is full of fair decks like RUG with
Lightning Bolt.