The first time I performed stand-up in front of a real audience was at a high-school talent show. Every single other act was either dancing to pop music or lip synching to pop music. This allowed me to be the most entertaining act by a factor of about 5 trillion and the resulting self-confidence boost set me on the course that made me the person I am today.
So in answer to your question: the point of lip-synching at a talent show is because the world revolves around me. Fortunately for everyone that means it's no longer necessary so all those dumb girls will have to either develope some talent or stop performing in talent shows.
I fronted a band doing "Funky Bitch". The mic died before the act and I had to stand at the edge of the stage and scream. I was voted most likely to be a musician or something similar. I am a network admin.