> which is institutionally thought of as unacceptable That's not it at all. The goal of hiring is simple: maximize the effectiveness of the company by hiring

> which is institutionally thought of as unacceptable That's not it at all. The goal of hiring is simple: maximize the effectiveness of the company by hiring people who are the most effective at least cost. Typically, the hiring manager thinks about what he needs and reduces the hiring question to: "For this role, we need a person with these skills or better, and we're willing to pay this amount or less." Then you evaluate candidates to determine their effectiveness. Many factors impact someone's relative effectiveness: if they take time off work for any reason, then they are less effective than someone who is equal in other ways but works full time. You simply get more weeks of effort out of them for the same pay - it's really simple. It has nothing to do with being "unacceptable" so much as a "bad deal for the employer". Imagine that you're considering two candidates, one who you believe will work full time, and another who you think has 25% chance of working half-time (while being paid for full time) over some period. The two employees are equal otherwise. The expected value of the first worker is 100%1.0 = 1.0, and the expected value of the second worker is (25%)(0.5) + (75%1.0) = 0.875. Thus by going with the first worker, your expected outcome is 14% better. Imagine that the second worker is 10% better than the first. Then his expected value is (25%)(1.10/2) + (75%*1.10) = 0.96, or still worse than the regular worker. The worker who is 25% likely to work half-time must be 15% better in order for their expected value to equal a normal worker. The results change rapidly if they are more than 25% likely to take time off, and if they work less than half-time. If they are 25% likely to stop working completely, then they have to be 33% more competent in order for the expected value to equal a regular worker. All of this ignores the practical complexity of employees who take time off work unpredictably. The problem is that for the company to function, the job still needs to get done, which means burdening other employees, or hiring more employees - but if you hire another employee, then they won't be needed when the first employee comes back, and they are by law entitled to their same job. A simple rational analysis shows that workers who work full time have a better expected value for an employer, and are a lot simpler to deal with because they're predictable and you can plan around their schedule.