Regardless of the optical quality of the lens, I never understood the 28mm focal length, especially as a prime.
It's too wide to be a 'normal' lens or for environmental portraits, too wide to be particularly useful for stitching, but not wide enough for the landscapes, interiors amd other things you'd typically use a UWA for. It seems to be a focal length that sits better as a step between 24mm and 35mm on a zoom lens, to be used for exact framing of certain subjects where you can't, or don't want to, move the camera or the subject, rather than something that's particularly useful as a prime in its own right.
In addition to Bernard's reply I requote below, I will add some words and apologies in advance if I mention stuff you already know...
Why primes, back in the early film era they were the best, older zooms were limited and awful in optical quality in general...
Primes are also smaller and or allow a larger aperture than an equivalent zoom for those specialising to a fixed focal length...
Why large aperture, it gave more flexibility on film choice, it gave a brighter viewfinder image, it helped achieve critical focus before stopping down in an SLR. It could allow some subject isolation wide open and a softer effect if needed...
Why 28mm, 28mm is considered the widest prime before you have the dual challenge of controlling your verticals and getting to close too a human subject being shot. It became a classic reportage lens the world over and the old Nikon was most sort after. It is just easier to use than say a 24mm which is too wide for that fast moving work where you want to be part of the scene, amongst those your shooting, and get all the surounding action in... (I don't mean selfy)
You mention 24mm for landscape and it was the classic lens for that in its day. 28mm just looks wrong for those types of shot.
24mm can be used with care if you are shooting people you know and have time to set up a more dramatic effect than can be achieved with 28mm
As Bernard also mentioned, 28mm is a great wide for street photography for the same reason it was popular with news reporters...
Why did Nikon release this now, as you hinted why this lens, less demand means the last to get replaced and it has been a long wait for some Nikon users who have been waiting for this day for years... I bet the ones that love this will not hesitate to buy, despite the high performance of some modern 2.8 primes in that range...
Is it needed in the digital age, well it is if you want the aperture and overall lens size, a zoom of the same aperture if made will be too big and heavy for the typical tight in use it would encourage...
Some folk are still passionate about certain focal lengths and will avoid zooms as they encourage the lazy framing you mentioned. A tool for a job a certain look and feel to the image only that focal length can deliver if the full image is uncropped...
Why not 35mm, some find 35mm boring some love it and find it much easier to use. The effect is very different, a 35mm almost has the look of a standard lens in some shots, and is just not wide enough when needed...
All personal to how people want to shot...
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In terms of lens design also, 28mm is pretty much the widest you can use and still get sufficient subject isolation over the background. You have to get way too close with a 24mm f1.4 or wider.
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