Why isn't everything HD?

With all the new TV's and their clarity issues, why aren't all stations available on HD? I would think they all would want to change to this feature since it is a selling point for purchasing. While digital is fine, HD exceeds digital. I just don't get why all stations are not available in HD. Can someone offer... show more With all the new TV's and their clarity issues, why aren't all stations available on HD? I would think they all would want to change to this feature since it is a selling point for purchasing. While digital is fine, HD exceeds digital. I just don't get why all stations are not available in HD. Can someone offer a good reason this is not so?
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