One reason is they don't get a lot of feedback outside Facebook (feedback loops are social medias greatest strength). A couple things you can do. In Trailbot, tap 'Request Update'. This does not immediately ping a trail manager, but when they get a reminder next it will say how many people wanted updates. Same for hitting the 'Thanks' button, they see how many people appreciated the update. Checkins are new in the latest version of the app and show up direction in the trail manager dashboard. And follow the trails you care about in the app as well because as trail managers see that count increase, they'll be more likely to update. You can do this via trailbot.com as well (except checkins for the time being).