I trying to think of the best way to say this so it doesn't sound stupid.
Putting on a professional karaoke show of my caliber takes much work and concentration. My concentration face unfortunately isn't normally an ear to ear full tooth smile. This can be from many factors.
First and foremost I am constantly scanning the crowd looking for A$$HOLES and troublemakers. This can include people not interested in karaoke and more interested in getting drunk and acting stupid. If and when I see these people which isn't often but it only takes one...my concentration face is not smiling about it.
Also during my show I am constantly listening to and concentrating on the mix. Even though I could be carring on a coversation or loading songs into the queue.
Next I am scouting the crowd for the next singer in line to sing. This can mean looking over the entire crowd from wall to wall or outside. Then I have to walk to them fighting the crowd with the microphone.
I could be experiencing technical difficulties that you don't know about, that I am trying to work through.
I could be pi$$ed off because of some jerk causing me a problem. Or because someone is complaining way too much. I could be mad because people keep changing their song 30 seconds before they sing. I could be mad because I can't find the next singer so I need to find another singer in 30 seconds to sing next. None of which makes me want to smile.
I wouldn't be doing this for 18 years if I didn't find it fun. While I do joke and laugh with people during the night my last concern is worring about if I'm smiling enough. There are also people with different facial features. Some people look like they are smiling even if they are mad because the corners of their mouths actually turn up. Some people have lips that are straight across. And some actually have the corners of their mouths that turn down. Mine turn down. Even if I'm smiling my mouth curves up to look straight.
I am constantly worried about the crowd safety. I am constantly worried about making every singer sound their best. I am constantly worried about putting on a professioanal quality show. If these all come together properly I'm happy. I may not be smiling ear to ear but it doesn't mean I'm not smiling inside.
I take my job seriously. Most KJs don't. I'm very proud of my finished product. Most KJs aren't. My lack of an ear to ear smile could be a trade off for a high quality show that you like to attend. Love me the way I am.
My concentration face means I'm doing my job as good as possible and it's all for your enjoyment.
it when people think they can just walk right up to me and start visiting like it was old home week or the like. I keep telling my wife that I'm going to put up a sign which reads "Do Not Speak to the Operator While the Vehicle Is in Motion". You know, like you see over the bus driver's head?
Maybe I'm not smiling because I'm biting the crap out of my lip. 
