I am a manager at a mid-sized (~100 employee) software company. We are fortunate to attract many employees for whom coding is their one true passion, and our products are cool enough to them that they genuinely enjoy hacking on work-related code outside of normal working hours.
There is no overt pressure or obligation to work extra (we set deadlines conservatively, not assuming that many employees are going to work above-and-beyond, and have explicitly banned after-hours email/communication), and much of the extra work is clearly done just for fun (e.g. someone learned a new framework for fun in their spare time and ported some of our existing code to it, which dramatically improved performance).
Naturally, employees who live and breathe code 24/7 (the “enthusiasts”) are a lot more productive than employees for whom the job is just a paycheck (the “9-5ers”), and thus the enthusiasts advance in the company a lot more quickly than the 9-5ers. The latter have complained that our company suffers from a culture of overwork, and that the only way to get promoted is to basically live for your job. Our target promotion schedule is well within industry norms (2-3 years between title bumps), but many of the enthusiasts manage to advance far more quickly (e.g. one exceptional person went from junior engineer to principal engineer in 4 years, which amounts to 1 title bump per year).
What should be done to convince the 9-5ers that the current incentive structure is fair, and is not overwork? It has been pointed out that our engineering workforce is overwhelmingly (~70%) male in large part because the enthusiast mentality is not compatible with childcare obligations, which unfortunately fall disproportionately on women, so making 9-5ers happier at the company would go a long way towards evening the gender imbalance. (We do offer 6 months of parental leave, and there are proposals to increase that to a full year.)