I think, quite honestly, they are the stupidest things to to have setup at a wedding. I think it's gimmicky and i think the photographer who sets one up would be much better served watching for natural interactions between the guests at the wedding and capturing those. I'll leave the gimmicky/novelty sideshow (no matter how many "extra dollars" it would make me) to others and concentrate on getting shots of the bride and groom and their guests NOT acting like drunken jackasses. I'm sure friends will get plenty of those later on their point and shoots.
I would guess that you havent shot that many weddings? Maybe when you have more experience you will be able to see the logical space a photo booth fits into during the wedding day. It doesnt have to be gimmicky or detract from coverage of the bride and groom, its just an addition to the days coverage that in my experience many bride and grooms enjoy having.
I dont think any B&G are gonna hire a wedding photographer based soley on them offering a photo booth but its an added extra that is another hook to get people to book you in the same way that good albums or other things you offer additional to the photos are.
Everyone is entitled to their own opnion of course but I think yours is being formed too quickly.