I also find myself in this situation a lot, expecially now that I'm in a country that is really closed to this sort of thing. Everyone wants to take advantage of my presense and argue over who gets a reading first. In the States, my response was usually, "I don't have my cards." Wasn't that a lie. Then my friend would betray me again and pull out some playing cards and say, "It's okay, you said you could read these just as well." *strangling noise* I've learned by now to just ask them to cut the deck and pull a card, and I'll tell them what it means. Over in 2 minutes, and their own attention span (shortened by the alcohol) sets them on another path.
Why do I dislike this to begin with?
I'm going to be selfish and say that I go out to socialise. One reading, even a three-card spread, usually takes over 15 minutes for me, and ALL of my attention goes to that one person. I'd rather not spend my whole night in a dark corner of the booth focused on one person with my beer getting warm when I came out to meet new people and have a good laugh over a drink or two.
Plus, it draws a crowd. I sit there doing a reading for someone, and his/her friends (and strangers) crowd around to hear the dirt. During the course of a reading, I ask questions as they appear in the cards. But they're personal questions, so I don't want to make the querent answer in front of an audience. I've done it before, and I just get denial after denial (when I should've gotten confirmation) because 15 other people were breathing on the cards. That's not how a reading is done.
Then there's the usual problem of people wanting to prove how false it all is (but sober people want to do that, too) and that's not fun to deal with. Music and other people talking are distractions (I have a tendency to keep one ear on other conversations, then interrupt the reading to jump in on the other topic). As other have pointed out, the novelty of being a circus sideshow isn't fun to deal with either. I don't like arguing over free choice vs destiny, lives set in stone vs making your own decisions. I especially don't like answering the question that always pops up, "Do you really believe this stuff?" Yes, I do, and if you don't believe that I can help you see yourself, why are you asking for this reading?