Reason #1: Underestimating yourself! Smart + witty = can be a bit intimidating... maybe you're accidentally going for guys who are easily intimidated. The small fry do not want to date the big fish. So go for the BIG fish. The smart ones. You know, guys with a brain.

It's like this: Do not try to sell custom car parts at the farmers market.

Take what you have to offer to a place where the fellas are looking for it. Taking your goods to the club, where the mans are all after the hottie-of-of-the-week, isn't going to get a ton of bites of the sort you're probably after.

My neighbor (46 year old dude, quite the player back in the day) told me last time I was whining about not getting any play at the bars, "You make dumb boys feel dumber. You wanna date them, stop using big words. You want to keep acting like yourself, go hang out with guys who appreciate that. And for God's sake stop whining."

#2: Subtlety does not always work on men. Sometimes ya just gotta bonk em in the head to make them pay attention. Just for shits and giggles, next time you're out with just one girlfriend (won't necessarily work if you're out with the whole crew, can be intimidating), go hit up a restaurant bar. Not a club where it's like the meat market, but an after-work spot, like a sports bar and grill, where the professional dudes stop after work, and just straight up send some hottie a drink. Be bold. Oh- and a spot like that, see if you can't toss together an outfit that's both professional and feminine... like an interview suit, but the interview is for a boyfriend...
Have fun!