The point of karaoke isn't to sing good, you just get blackout drunk and embarrass yourself, but it's cool because everyone else is doing it too. And maybe there's one old guy at the bar with an amazing voice who blows everyone away with a Frank Sinatra number, and you all admire his ability but you don't feel competitive about it.

At least that's my experience with karaoke. If people demanded a good performance, it would totally ruin it. ( ´ω`)