LaTeX isn't just for users, there are also people who are developing packages or classes. And since LaTeX doesn't even offer the luxury of arrays or hash tables

LaTeX isn't just for users, there are also people who are developing packages or classes. And since LaTeX doesn't even offer the luxury of arrays or hash tables natively, LuaTeX is very a refreshing change. My company is using their own LuaLaTeX class extensively to produce hundreds, if not thousands of reports per year, and features like automatically computing the CVSS base score of a CVSS vector will take a couple of minutes in lua, while it will cost you several days and a bunch of gray hairs to do in TeX. It's only the developer who has to know any lua though. It's completely transparent to the user.