What's the Deal with Voice Talent?

It is kind of surprising when you discover a business who has an advert on the market and who obviously did not employ the perfect voice talent. You question what the deal is, why wouldn't they take the time to employ someone to do an effective task? They waste time and money of making an advert, they pay for the radio air time, yet their voice over person just doesn't appear to get what the product is about. They do not sound convincing when they're talking about the product and they don't inspire excitement either.