I think it’s a size thing. At some point it just doesn’t make sense to put in a lowered ceiling, because it costs a lot of money for no purpose and still looks like shit. Large stores in Europe also have visible airducts and supports etc.

Also, some malls have rules for what tenants are allowed to do with it, either for safety reasons (water sprinklers/fire alarms) or just because they don’t want to repaint or remove whatever the tenant did with it before they went bankrupt.