It is as difficult getting new people in a community and building a community as it is in getting established as an individual on Hive. Right now there are a lot of communities on Hive, most have a hard time getting established.
An example is I follow 5 Photography Communities. They have from 0 active users with 140 subscribers, (the low side), to 291 active users with 1049 subscribers. Pretty small numbers when you see the amount of photography related post. The large catch all community of GEMS has 1656 active users, and almost 6000 followers.
Remember though Hive Block Chain has only been active for about four months, it is still in its settling in phase. As for getting your community seen, peakd has worked on getting a post promotion system working where you pay to have your post/Advertisement moved higher on the explore tags and feeds list.