Golden handcuffs is definitely one reason. You'll also find that most guys in the left seat are more "stabilised" with family etc.
If you come here as an FO, we now have the age limits for upgrade plus a reduction of expansion (as opposed to a contraction) with a net gain of, I think, 1 or 2 a/c this year which could mean a glut of FOs waiting to upgrade in the future.
Until recently, the management seemed to be trying to be more reasonable in disciplinary terms but that is a variable and you have no union to argue your case.
It's not all bad but you need to very carefully weigh the pros and cons. The golden days of expansion are past, we are in an "adjustment" phase and that doesn't usually mean good things for any workforce.
Personally, for those who chose to come, I now see EK as a career transit airline rather than the end game that it was when I joined. How the mighty can fall.