There are a lot of famous singers that don't dance on stage. Neil Young, Kurt Cobain, Geddy Lee, Bob Dylan. Having a sense of rhythm and a good ear just aren't enough to make you a good dancer.
Your examples of singers that don't dance on the stage don't prove that they can't, but just that they don't want to.
I was asking about someone who is a well known singer but actually tries to dance but really can't and it shows.
And again, we are talking about correlation, and not exact match of skills. So it wouldn't mean that a great singer is automatically a _great_ dancer, too. Just that if someone is really good at singing he is likely to be pretty good at dancing but not necessarily exactly as good. Maybe that's part I didn't articulate clearly earlier.
And you were with them when they casually danced in clubs and you saw they actually can't dance? Or you are around that that kind of musicians that actually never ever dance for fun at their leisure?
Went to many music festivals, clubs, dances with them. They couldn't dance. They weren't incapable of learning how to dance. They just weren't automatically good at dancing because they were good at playing music.