so why are wind farms getting built?

Many wind farms are being built because of state laws that require utilities to include a certain growing amount of renewable energy in their mix of generation sources.  Many others are being built either because the utilities expect to be required soon to have more renewable energy in their mix, or because in the particular area, the projects are cost competitive.  Some projects are being built to sell the power into the “spot” market, and are likely relying on the prospect of REC revenues from the voluntary REC market for their required return on investment.