Does anyone think Apple is going to address this white background issue?
You would think by now they would know the health dynamics of bright white light &/or color vs health/overall. In other words, why did they do it in the first place? Are they ignorant/unaware of the health issues? They have the experts involved in design in order to teach them what they may not yet know, don't they?
What really bothers is you really start to realize how bad it is when you invert colors and look at the settings menu.. You feel your eyes just relax and feel good... This is how it should be..
Exactly. Little story of what I learned in the past year:
1. Always hated dark website backgrounds... UNTIL !!! I began creating photo-blogs & read that pics always look better on black backgrounds. So I tried dark themes, & sure enough, pics look fantastic against black backgrounds. (Like old-time construction-paper photo albums from the 1950's. They were always black pages for a reason!) Point being: Attitude Changed 180 degrees re black backgrounds. That was the first big revelation.
2. Enter family member gets cancer so I start researching. One thing I learned was re BRIGHT WHITE ["blue"] LIGHT & the cancer connection. The pineal gland is above/between the eyes. It secretes melatonin. Melatonin not only produces deep sound sleep but also is a cancer INHIBITOR. Bright white light STOPS the pineal gland from producing melatonin. Night Owls, Night Workers get more cancer than other people (they are in lights more). Blind women don't get cancer as light never goes into their eyes. Etc. Seeing-Women are more susceptible than men due to hormone makeup. Staring at bright white computer screens & now cellphone screens (& TV screens, etc.) all day & into the night is inhibiting everyone's pineal gland from producing melatonin, the needed cancer inhibitor & sleep-inducer. For more info about this, former-GE-Lighting engineers have a site, LowBlueLights.com (Blue referring to the bright white lights, like fluorescents & tanning beds & light-tables & computers/cell screens, etc.). Check their Cancer menu tab for studies, etc. Tons of research there. They also offer amber shields for TVs, computer & cell screens, or amber eyeglasses, etc., to "fool" your pineal gland that it is Dusk outside so your pineal gland will begin producing melatonin even if you're staring at a bright white cell screen at midnight. Not cheap; cheaper ones at Amz but some reviews there saud, "You get what you pay for" & that the Amz amber glasses were shoddy el cheapo whereas the ones from LowBlueLights were better. I haven't tried their glasses but did get the little iphone amber screen ($13) but it was a pain to put on properly even though I liked/got hooked on the amber color/blocks the whiteness of iphone & wanted to leave it on all the time.

I Plan on trying the glasses next (approx. $35). -- Point being: This was my 2nd big revelation re bright white light/color, the pineal-connection!
3. A few months later was reading wordpress forums, person asking re themes, colors, etc., & one of the longtime WP experts replied, "Dark Color Backgrounds are Easier on the Eyes, Less Stressful on the Eyes!" (Just as you said above!) I was like, wow, there it is again, the 3rd time I'm hearing about this in the same 6-9 months timeframe. -- Point Being: A lot of people know about this, so why doesn't Apple?
Why make it uncomfortable for the user?
Exactly! How could computer companies in business for 30-35 years never have come across scientific & medical studies re how damaging bright white lights & screens, & bright white colors are? SURELY THEY MUST KNOW BY NOW!?! With Apple's billions they never hired someone to research these things? You have to wonder what is their motive for making bright white screens even whiter by removing all color & adding all white instead?
And fwiw, I keep my 3Gs screen/brightness all the way down to like 2% & it's still too bright, so I use the White on Black option as much as possible (it messes up all icons & photos, but for text/reading it's a huge improvement. Gorgeous gold & black, too, on older ios).
HTH!