I’ve worked with various venues throughout my career and the amount and nature of the support they offer has varied greatly. Is marketing support something event organisers want and should expect? I would also be interested to hear of any venues doing a great job.
I think this might vary across different sectors of events. E.g. in the music industry I think it’s probably pretty common for venues to support artist promotion, but that’s also because venues often have a fan following in their own right.
Outside of music I think is probably a lot less common. That said, venues that have a community associated with them will often help market your event if it’s of value to their community. Google Campus springs to mind here - if you host an event there they will promote it to all campus members.