Most venues expect the artists to promote each show — that’s built in with every gig. You're being booked because of your fanbase. Unless the venue is also a bar that has a built-in crowd, it depends on the music to fill the room. However, no venue should 100 percent depend on a band to promote the show.
If a venue's social media pages are inactive, the managers don’t hang posters, and they have a reputation of never promoting, that isn’t a good sign, and you'll want to think twice before booking a show there. A good venue will post flyers on its Instagram, create Facebook events, share YouTube videos of the performers as a show approaches, put up posters in the windows, etc.
Venues need to make money, too, but if a venue isn’t willing to lift a finger to promote, you might want to really ask yourself if it’s worth it to perform there.