Time out for maternity here means that engineer's work on the project will need to be picked up by someone else for the next six or so months. Someone else has more of a workload. Schedules won't be slipped to accommodate having one person on leave. So, maternity leave is quite a good benefit women have - I'm not against it because I believe it's valuable for raising children and improving society.
I think the so called work ethic in the US has historically been that women were a bit of a nuisance in the work place. In the late fifties, when they made advancements in the workplace away from the traditional women's jobs, secretaries etc, they were often seen as taking away work from men, who were the traditional breadwinners in a family. Then employers had the financial burdens and inconveniences of the maternity issues of time off and in some cases women just left the workplace to then raise a family. This in essence wasted resources training them to have them leave, whereas men usually stayed at the company for a long time.
These are just generalities but I remember it pretty distinctly even into the later 20th century. There was also the good old boy network with the sales guys and other jobs where women had the jobs but were sort of excluded from the activities by the boys.
Due to affirmative action and human resource departments as well as societal changes this mostly disappeared but there are still a few remnants and neanderthols floating around.
In more socialist countries it's even advanced to the men getting maternity leave and other benefits, where the employer just has to have more people employed probably to cover the costs and absences.
But this is a phenomena that the US is going to have to grapple with as the world changes. A better workplace and lifestyle benefits and perhaps a bit less profit chasing.
Is the workforce an asset or a liability. Right now I think a lot of corporations place employees on the liability side of the ledger. An unfortunate cost they have to deal with.
While in some other countries with very successful economies the people are just treated better.