Also note that the board is very often composed of current/past/future CEOs of other companies.
I believe German CEOs typically make around 1/3rd of what American CEOs make (having trouble finding the source on that, but that's the number I've seen cited before), possibly in part due to these laws.
The requirement for half representatives for company's employees is for (secondary) supervisory board of directors, not for (primary) management board.
At best one might say a vote against would be to sell the shares, but if public companies broadly all overcompensate their CEOs then it's this tension between leaving most of the market or investing in companies that might make money despite overpaying.