I just put alu nipples in a new wheelset but a) I can fix it when it goes wrong and b) I’m a known idiot. For everyone that doesn’t fall under at least one of these categories, brass is just the way to do it.
(with proper spoke depth, and decent parts outright strength with alu shouldnt be an issue, but when they crop up in cheap/oe wheels you can’t really assume either of those things is true. The real bollocks is corrosion and seizing- it’s an evil combo, they’re both more likely to sieze, and more fragile when you try to unseize them, so you come to true a wheel and snap.)