The answer to all of your "follow up examples" is this: they shouldn't

"Why on earth should engineering majors study optics, when so few will work with optics?"

They shouldn't be precluded from engineering for being bad at optics. If they need to learn it in the future they can... or someone who is good at optics will do it.

"Why should a computer science major study operating systems, when scant few of them will actually work on an operating system?"

They absolutely shouldn't "study operating systems" unless they are working on some kind of operating system science. What they should do is be proficient at using a computer enough so that they can analyze their data. Perhaps more computer savvy for physicists and less so for cell biologists.

"Why should English majors study poetry, when so few will become poets?"

Your one good example. Studying poetry would actually benefit someone writing prose if only to allow their prose to be more poetic. However, a lack of poetry knowledge shouldn't preclude you from being a writer.

"Why should Business majors study economics, when so few will actually become economists?"

Once again... knowledge of economics probably can help businessmen. Although you should remember that Bill Gates never finished college and most likely never took Economics and that didn't stop him from being the most successful businessman on the face of the earth. Steve Jobs is also a dropout, as well as Michael Dell, Paul Allen, Ralph Lauren, David Geffen, Larry Ellison, and Andrew Carnegie to name a few. No one told them that they couldn't be businessmen because they didn't take Econ 101.

'Why should a home owner buy fire detectors, when so few will have their house burn down?"

This has nothing to do with organic chemistry and medical school. This is akin to saying how could someone be a doctor without taking organic chemistry when people always look both ways before crossing the street. Its a good idea to have smoke detectors but not having them doesn't prevent you from living without burning to death in your home.

"Why should people buy the Journal, when it publishes such stupid crap?"

Who knows?