Yeah, the "why" was conspicuously missing from this article.
I looked and could not find any official reference to a home theater installation license in Connecticut. I would've expected to find it here: http://www.ct.gov/dcp/cwp/view.asp?q=461650. If the article is referring to licenses required for low voltage work, that's a license that's required in other states too (including California).
For the Louisiana florist licensing, the best I could find is that it was enacted in 1939. I couldn't find a reference to the actual law or to whatever its origins were. I found plenty of articles that were critical of it (https://gpnmag.com/news/louisiana-florists-need-license/, https://www.legalaffairs.org/issues/May-June-2004/scene_joyc...), that didn't seem to share a political bias. Given the age of the law and its uniqueness, it does kinda stink of protectionism.
Past articles on onerous licensing across the country (https://www.nytimes.com/2014/05/29/opinion/why-license-a-flo...), have been written by Morris M. Kleiner, who appears to be closely related to the Institute for Justice, which is a libertarian law firm that has been filing lawsuits against states over their licensing laws for years. The IJ is ultimately the source for the submitted article in The Atlantic.
So this is a political article, and although that doesn't mean it's wrong, it'd be really nice to get some more objective background information on these licenses.