The UK has a show dedicated to a competition to see who is the best host of a dinner party. (come dine with me). Its a great show but shows the culture. The poor host has to pay for everything, prep, cook while entertaining the guest and usually put on some show or activity for extra points.
Yeah, you're expected to help in some way. The idea being that a party at someone's house is likely an inconvenience to that person so if you want more of that to happen you should make sure the host feels barely any pain. Even if you don't bring anything to the party you should be helping place the table, carrying furniture, doing dishes...something.
People who don't help at all aren't well perceived and will probably not be invited again.
> Host Forbes Robertson, the only man in the group, is Ayr's answer to Donald Trump, and his menu plan includes pigs' trotters, which don't appeal to his guests