I would argue the cowards who refuse to ever stand up to employers are the cause. If you aren't able to push back on your boss, you're fucked regardless of how many hours I choose to work.
There is a problem in thinking any one thing is "the cause". It's a multi-faceted problem of many self-reinforcing causes. The comment above talking about "shifting the culture to make it that much more acceptable" is a nod to the subtlety of what contributes to this.
All parties, employers and employees both, need to see how they do this.
I see no "nod to subtlety" as you claim. All I see is a claim that one employee's overwork is what enables the boss to force you into overwork.
For this to happen one needs 1) routine culture of overwork, 2) and employer who leans into this fact, and 3) an inability or unwillingness to push-back.
If you solve for #3 you've made #1 and #2 irrelevant.
Calling for others to stop willingly work as much reminds me of an old film I'd seen as a kid wherein a new employee starts at a loading dock, and after his first highly performant day the old-timers come along and give him a talking to about his making them look bad.
You'll only look bad if your team and boss expect the "above and beyond" to become the new norm, and this isn't a rule. It is a result of shit conditions.
Just as expecting your coworkers to go above and beyond is bad, so is chiding them for willingly working harder than you.
I have seen it in very mundane things that are not nearly of the magnitude of consequence of this topic. And also, in big things, such as expectations around working hours and standing up to unreasonable requirements.
Perhaps one aspect is that if a behavior is perceived to be a path to success in an organization, it will be emulated, rightly or wrongly, consciously or not. It's important to create an environment where many can thrive.
Your point is sound. It's also more ascerbic than it needs to be.
But if what you mean is that employees have a choice between passively accepting the status quo or trying to act collectively to improve their conditions, then yes, I agree.