shouldnt have to run in mono? if a club's system is mono, its mono. there is no 'shouldnt have to' when stereo isnt an option. unfortunately for you this is how most clubs are. its like expecting itunes to run an .ogg.
the more you play out, the more you will see that you are making things difficult on the soundguy by expecting a stereo setup or that they can handle it. i cant totally speak for him, but im sure if you asked, dino would say that being a soundguy is one of the most thankless jobs you could have. why make things more difficult for the person doing the sound who is most likely getting paid a shit wage, who is in control of your sound and put them in a position where they cant do their job adequately? i personally wouldnt punish the guy who is just trying to do his job by throwing him a curveball like that when theres not much of a benefit to running stereo in the first place. that doesnt mean you shouldnt ask them questions and ask for more of whatever in your monitor or to turn up this or that, it means you're expecting too much of something that isnt necessarily the way they do things, and its going to be different whereever you go.
when you hear live music, there isnt really a point of reference for the people in the crowd that they can experience a stereo image. more often than not when youre in the crowd, you're standing on one side of the stage or the other. there can be dead spots in a room, the club could have already tried it, they might not be set up wattagewise to do it. whatever the reason, and more often than not, the soundguy, and the performer on the stage are really the only ones in the club that can benefit from something being in stereo, because you and the soundguy are the only ones in the club that are squarely between the left and the right channels. this is how it works unless you are playing in a place with a ridiculous soundsystem, or a small sound system. your best bet would be to talk to the soundguys when you get there and ask them if they run in stereo, and if they say no, to run your stuff in mono.