Yeast nutrients tend to be in a more labile form than in wort, so the yeast can utilize them more quickly and efficiently. Also, wort can be deficient in zinc, which yeast need. You'll be fine without it, but if used as directed, you may observe shorter lag times.
The Fiesty(sic) Goat Brewery est. 2007 & Clusterfuggle Experimental Ales est. 2009
Planned: Fat Man Porter, sLambic II, Brettennial Falcon IPA, Flanders Red, Orange Blossom Mead
Primary: Winexpert Riesling Ice Wine, sLambic I
Secondary: Flanders Red
Kegged:Black or Blue EyePA, Cherrywood-aged Crystal Stout,
2013 dump volume: ~2 gallons