First off, I love taking classes. Love the interaction with new people, and look for common ground during discussions that break out. Even taking "easier" classes is fun because there is always something new to learn or an easier way to do something. As for "cliques", "talker's" or "snobs" I don't let them bother me, I'm there for myself and don't need to impress anyone.
What deters me from taking more? The biggest reasons...time and money. I know that there are costs involved but many shops overprice their classes and then you have to add in the purchase requirements. Buying a pattern, I understand but smart shops would offer a discount on fabric (even a small discount) to encourage people to buy their fabric there but it shouldn't be a requirement. I'm already paying for the class and over the years have bought tubs of fabric from them, why shouldn't I be able to use what I have?
Luckily I have two local shops that offer reasonable class prices and buying the fabric there is not required. What deters me are the time schedules. I work full time and can't take daytime classes. The occasional Saturday class is ok but 3 or 4 hours out of a Saturday takes away from home and family. They need evening classes and maybe spread them out, maybe every other week. Having evening classes could be a draw for younger/newer sewers.
Space is an issue when taking classes; is the class room open and easy to get around? Are there cutting tables and ironing boards set up or do we have to bring our own?
What kinds of classes? Ask what they would be interested in. Different skill level classes or offer a quilting class from beginning to end for new sewers.
How about doing a "donation" class? What I mean is projects that will ultimately be donated to some charity. You can charge a small fee for the class portion then offer the same amount in a store credit. One LQS has and all day sew for pillowcases, $5 for however long you can come and then you get a $5 store credit.
Gosh, didn't mean to write a novel! There are so many reasons people do or don't take classes. Mainly you need to ask what they want or ask them for suggestions. Do remember that the people taking the class are "customers" and often to draw in new customers you need to accommodate them to build up a larger clientele.
Good luck and let us know what you decide to do!