Heck I will toss in my 2 cents worth, mainly because I have brought up the subject before.
Jwb and Metis are both taking to the same conclusion, just taking different tact's to get there. JWB would like people here now, and let the reason they are here come along after the people.... Metis is seeing the gear brining in people, and the more utility they have, the more folks we will draw.
Both have good and bad points, figure them out yourself. I take yet a third tact and say that the reason we have so few (insert your demographic here) is lack of promotion, lack of hang out space appeal, and a bit of apathy on our members. Walk into the classroom tonight, look around... what you will see is parts, leftover project bits, coffee and beer containers, and a mess.
Regardless of your demographic, this space as it is now, is not set up to host a group that wants to talk about subjects other than those we have left out.
We have no way for a group of twenty to see the makerbot print a thingverse file, the one seat that faces the other seats is a couch that last time I was there had somebodies project taking up half of it. The Trash and counter in the classroom are often cluttered, the bathroom would make some Horror Film depictions pale.
The space is a workshop, yes I know that, but with no full time cleaning staff, two days after we had our last Cleanup Day, the office had fallen back to what it was, the classroom was disheveled and within a week, nobody even knew that a clean up day had happened. Now alot of people worked hard to clean the space last time, and as a result I was not going to ask them to do it again.
Now for promotion, I have seen the last 9 Pumping station one video's, the Quad City guys (much smaller group) out produce us on blog posts, and until recently our own blog mentioned that we had a zip line race 4 weeks ago, but did not ever mention the results.
If you want people to show up, you have to give them a reason, and Classes / Demonstrations are part of it, having a space they would want to walk into a second time is another. Each of us is an Ambassador for TCMaker, like it or not, you are. You need to talk to your friends, co-workers, the guy at the Ax Man, whomever and mention the space, our group and that they should stop down. Carry the business card, or a brochure around and give them to people.
I used to hit craigslist for stuff for the space, and each posting I included a link to the group, and if I met somebody I told them about us and that they should stop down.
We need to promote ourselves, and to do that right we something that appeals to people who stop buy.
That is my take on it, and while I have given up on the quarterly clean up, I do try to follow the post that metis has elsewhere, and each project has time alloted for clean up, and days like today where I have no real project, I will spend some time cleaning up something while there. And I will try to promote the group to people when I can.