Sometimes we visit such picturesque locations, it's tempting to post images of the location even if we didn't actually attend the event (or the event hasn't happened yet).
Meetup only allows a limited number of photos per event album. And we want the spotlight to be on members who participate in our events. Now that our group has grown, allowing everyone to post their favorite location photos, even if they don't participate, is filling up the album and taking the spotlight away from members who participate in our events. Organizers are having to delete photos from non-participating members to make room for people who attended. Albums are now limited to photos taken at the scheduled event, rather than the location in general.
Also, we politely request that members limit their uploads to their favorite 5 or 6 images, at least on the first few days after the event.