All Day Happy Hour?

Don't know why I'm on this alcohol bender, but here's one more.

SC's State House is getting ready to vote on a bill allowing all day drink specials (but still not less than half-price), as opposed to just one hour.

Beyond a rant long time readers (Hi Ma!) can now probably write for me, I'm stuck trying to figure out why the first law exists in the first place (and why the "not less than half-price" condition). My first thought was that it was some kind of prohibition left-over, but the fine, "at least three months in jail and a fine of $100" seems more modern. Anyway, the only thing I found particularly interesting about this is that I didn't know that the concept of "Happy Hour" was bracketed by law.