Stuff that works well in homes often is a lot more complicated to implement in restaurants, where you're: a) constantly fighting grease buildup and hard-to-remove dust that clings to greasy or damp surfaces, b) often have a profit margin of like 2%
if you're one of the successful ones, c) aside from looking clean, you have to worry about pest control, fire codes, health codes (you can't have built-up dust falling in people's food, d) etc etc etc etc. Also, how restaurants look is as, or in some cases more important than the quality of the food. A good, attractive, practical restaurant design is one of the things that can steer you towards success or failure. Much to many chefs chagrin, hip and attractive restaurants with shitty boring food are often more profitable than ones that only focus on the food. Marketing is annoyingly important.
With, floors hardwood is a hard surface (so only mildly sound damping) so they're not too bad for cleaning and health stuff, but are expensive to install and take a lot to maintain if the worn-in look doesn't fit the aesthetic. Low-pile carpets can be shampood inexpensively for medium-term maintenance and replaced comparatively cheaply in the long run, but take a lot more effort to keep clean when someone drops a catering tray full of crème caramel and something with a port wine reduction.
Artwork: anything that you'd want hanging on your walls is either going to need to be a print or covered with glass or plastic because it will get ruined otherwise.
Acoustic panels are usually pretty ugly, difficult to clean, not resistant to pests, are a fire liability if coated in grease, etc.
Curtains definitely are definitely viable, but if you've got enough of them to really impact the sound level, they probably need to be expensive ones, and expensive curtains can't just be tossed in the wash and pressed on an ironing board.
It's not like they aren't effective, they're just not nearly as easy to deploy or maintain as they are in homes or offices.