When I first entered the workforce I would go above and beyond because I assumed there was an unwritten agreement between employers and workers that going above and beyond would be recognized by management and result in raises and promotions. I soon realized that in reality most employers just thought I was a sucker who they could “reward” with more work for the same pay and a pat on the back if I went above and beyond the norm.
Perhaps it was somewhat true for previous generations that rewards were tied to performance without legally binding commitments (i wouldn't know as I only entered the workforce fairly recently), but based on my own experience and exchanging experiences with people around the world, it certainly isn't true now.
So from now on, we're not taking an employer's word for it that going above and beyond will result in raises and promotions, we're going to need that in writing.