What's the Deal with Voice Talent?

It's kind of surprising when you come across a company who has an ad out there and who obviously didn't hire the right voice talent. You wonder what the deal is, why wouldn't they take the time to hire someone to do an effective job? They take the time and expense of making an ad, they pay for the radio play time, yet their voice over person just doesn't seem to get what the product is about. They don't sound convincing when they're talking about the product and they don't illicit excitement either.