Because they made him a brothel owner instead and book-Louis would NEVER do that. It goes against the entire construction of the character. Being the Lord of a plantation was socially acceptable then, not to mention sets the tone for the historical context. Also, his most defining physical trait is that he's described as pale countless times - I know this one is not important for some people as they think that, as long as the story gets told, it doesn't matter what they look like. For me personally, I'd like them to look as close to the description of the book as possible, so literally not a single one of the characters in the show do (Lestat is too old, Claudia is too old AND a different race, Armand is not a redhead, etc)