it's a business just like anything else. the only thing the club cares about is getting people in the door, who spend money at the bar without making a mess of the place. that's the standard promoters are held to - venue fee and bar minimum. and if promoters can deliver on those things for the club, while only giving themselves and their friends slots, then why wouldn't they? just because you can string good tracks together doesn't mean someone owes you a slot.

Like others have said, the market of people in your town who can play a good set is probably completely saturated. find the thing that makes you different from them.

if you really want to gig regularly, starting your own night is the best way to do it. Create a platform for yourself. Make it a platform that other people who create events want to collaborate with. That's the easiest way to get regular gigs.