But then again, why does Nikon need to make these lenses? They are slower, cheaper, cover a little more range... ugh. Nikon already has a $1000 70-200... it's called the 80-200/2.8D, lol. Why get a slower lens with VR and pay more?
Weight. When you're backpacking in the wilderness with your tent, camping gear, and spare clothes you need to minimize the weight of every little item. If you're only photographing landscapes, f/2.8 is useless and the extra weight unwelcome.
Even if you're photographing a group of animals or an animal in its environment, you can often get away with f/4. And if you're really photographing animals seriously, you'll probably have something like the 200-400/4 or 500/4, in which case since you can shoot with these at f/4 or smaller (you have to), there's no reason the f/4 would not cut it also in the 70-200 range in the same conditions you're working in. The f/2.8 is again weight in the wrong place.
I am a people photographer first and foremost and f/2.8 is slow for me, but I make do with f/2.8 zooms and faster primes. For me, the f/4 in the 70-200 or 24-105 would often be a problem and so I am not waiting for these. However, when I'm backpacking and photographing landscapes e.g. in Lapland, for sure the f/4 versions would be very helpful.
Also, some people prefer more range than the 24-70mm gives in a standard zoom. 70mm is too short for a head shot (on FX) so a 24-105 might be a good lens to use in the studio when working rapidly with groups and individuals. For me, again, no; I prefer the brighter viewfinder a faster lens gives and the more options in terms of depth of field and use of available light.
What nikon needs to concentrate on is their primes.
They don't. Few people use primes.
Those lenses you mention would certainly be appreciated by me, but we can't speak for the majority of photographers.
