Yay at more "I don't agree with your PoV, so you have never played cricket in your life" posts.
And yes, its not that difficult to leave the crease AFTER the ball has been bowled even as the non-striker. No one is saying they should not move. IIRC, Steve Waugh was basically running with the bowler when quick runs were needed in the super 6 game in the 1999 WC. The point is batsmen at either end have to ensure they have something behind the line till they are sure they can't be run out and if they leave, there is the risk of them being run out. Simple as.
I never found it that hard to ensure I had something behind the line even when I was backing up as the non-striker. And so do so many batsmen for so many thousands of balls. There is no question of "fairplay" nonsense here. The rules tell the batsmen to stay inside the crease or risk being run out. So don't cry if you do decide to leave the creae and someone runs you out.