Eye AF?

Three words to answer your question about the need for eye AF:
Weddings, pets, children.
Those scenarios are not necessarily fast-moving, and there is where eye-AF is most valuable. Imagine doing the portrait images of bride and groom outside. Put the autofocus point on an eye and it will stick there, allowing the photographer to concentrate on composition.

There are plenty videos on YouTube where folks review the eye-AF of the Z6ii. It's a wedding or fashion photographer's dream.

I would never consider using AF-S for landscapes (and some architectural situations). Manual focus is preferred since you need to have adequate focus near to far unless you are purposely throwing the background out of focus for effect.

With focus peaking so good, and accurate, manual focus is a natural for anything you want to control the focal plane for artistic reasons, but Auto Area Eye Tracking AF-C is really good for very shallow depth of field images. I do not use it in the studio because there, the background us controlled so fashion for full figure shots are usually done stopped down and depth of field is not a concern.
With the faster lenses and the slight movement of the shooter and the subject, AF-C Eye AF really does increase the keeper rate of handheld shots of people. The Z6/7 were also very good for Eye AF from firmware 3.0 and later. The one advantage of Canon and Sony that was promoted by the youtube influencers was the distance eyes were detected on those cameras but in real use, tracking someone's eyes at 30 feet is useless, especially when the Sony was tracking faster in the EVF but not at accurate as the Nikon that keeps it off until the eye is closer. Their focus peaking is not as accurate either so fast lock on, if it really is not locked on, is a hollow victory. I did a shoot for a jazz singer in a small club Tuesday, and my "old" Z6 did just fine in the dime mixed light source jazz club, only one missed focus out of 218 frames and that was my fault. Getting good focus is not a problem with these cameras, but many users are beginners and do know understand when different focus modes have an advantage and how good MF is on the Z body. There really is no excuse for missed focus with any modern camera and the youtube influencers ranking cameras based primarily on the EVF tracking indicator speed is a sure indication their income stream depends on promoting one model. They skipped over build quality, handling, ergonomics, color science, high fidelity EVF, weather sealing, etc to promote their brand based in how far out the EVF shows the camera detected the eye.
Stan
St Petersburg Russia

Visit my Nikonians gallery.

I used it just this week. My dog dislikes having a camera pointed her direction. Her ears go back and she may walk away. But she was very ill, and last Sunday could not even walk up the steps on our deck without a rest. We said goodbye on Tuesday, so this is one of the final images.

Using Animal Eye Detect and the rear LCD, I could engage with her and hold the camera at arms length about 15 inches off the ground. I was able to hold the camera in position to compose the photo and get the shot with the eye perfectly sharp. The previous 20 frames composed traditionally were either out of focus, her head was turned away, or her ears were back. I got 4 good ones in a row with Eye Detect. I was at f/3.2 and 50mm to blur the background. I used a silent shutter.

I consider it to be a tool. It does allow you to worry about composition or engaging the subject. That's not a tool you need for every shot.
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I have had my z6ii for a few days,used eye af on a dog works very well.

I’ve found eye AF to be most effective when shooting at or near wide open with a fast lens. The 85mm f1.8 is a great example. It can be hard to get the eyes in proper focus without it. For slower lenses or lenses that are stopped down, it isn’t as useful since focusing on the nose instead of the eye is covered up by the depth of field.

On a side note, I find all those YouTube autofocus comparisons very misleading. So many YouTubers would have you believe that Nikon Z autofocus is completely unusable and easily beaten by a ten year old camera. They effectively complain that it isn’t magic enough at being able to figure out what you want to focus on without user intervention. If they took the time to learn how to use it, they’d find that it’s actually very good.