Most (but not all) of the locals that come w/ cable, D*, or E* are available OTA where I live. But in markets where OTA reception is difficult, it's a problem that can't be overstated.
I honestly had no idea at first just how offended many people are at the idea of a company offering service w/o providing the major networks. But I now know several people who flat out refuse to get Voom because of the problem getting locals OTA in their area. It's quite simply a deal killer. No matter how many other HD channels are offered, if the networks aren't included then a provider is Mickey Mouse, bush league, a joke in their eyes.
My parents, too, will drop Voom when their 6 month term is up if locals aren't available by then.
At the very least, HD nat'l feeds are needed for Voom to survive.