That's because it has no hyper threading and lower frequency.
It does as hyper threading it just has a slightly lower frequency.
I'm planning to upgrade my i3 2100 to a Xeon E3-1230 V2 as it is pretty much the i7 3770 without the graphical die. I can get the Xeon E3-1230 V2 for around $10 more than an i5 3570k and since i'm not overclocking why would I choose an i5/i7 over the Xeon?
If you want a xeon cpu, get the Intel Xeon E3-1230 V2, it's supported in most motherboard, like the b75,h77 or z77.
That cpu is the i7-3770 without the on die gpu, if you don't need the on die gpu, get the xeon, also it's cheaper.