Why are homes powered by ac and not by dc current?

power station may also provide dc voltage with using of dc generator but it is not economical to transmit the dc voltage. Since the step up and step down of dc voltage is not possible directly using Transformers, we'll have to transmit domestic supply voltage (DC, as your inquiry). But transmission of a DC voltage over lengthy lines would result in a much less voltage at receiver's end.

So, considering the efficiency, economy and easiness, AC is preferred to DC.