Almost all planets discovered so far are in an unusual configuration: they are gas giants close to the star. The lighter gasses tend to coalesce first as the proto-star cools, and so gas giants usually will form farther out more often. There are probably far more of this configuration out there.
Ah, much the same way that our gassy aunt Ethel drives away all the little kids from the table at the annual family reunion picnic!Originally posted by DynaSoar
Gas giants close in will disrupt smaller, denser planets forming in the region where those elements coalesce, near the habitable region. The more likely case, with the gas giants farther out, means rocky core planets are more likely nearer in.