Not quite sure what context they say it. Maybe if a kpop group has been really busy, maybe had a just had a comeback and then also recently announced that they are going on a world tour.
And fans are like "they need to rest"
I have once heard that members of one group don't like being told that.
And it is a group that seems to be working hard.
Now I think of it. It kinda reminds me of when I'm at work and working 2 hours (which is of course little in comparison), and my co-workers are like "You need a break right now". Even though I don't mind working without a break.
EDIT: Oh wait, I can kinda relate to being busy, like if it was like back when I went to school and maybe had to do a lot of homework and stuff and feeling like "When is the next holiday going to be?". But thank goodness, my work doesn't involve me doing that kind of stuff.