I guess I was more curious about the cost/benefit. Given a well defined standard like POSIX, and the difficulty of swapping in a new shell into Windows, I wasn't seeing why you'd buck the well established trend.
Fish is my daily driver. I use it because it makes things I do regularly either easier, more memorable, or less error prone.
The primary use for fish is not scripting, afaik.
From a quick glance, nushell, like powershell, is strong working with pipelines of not-just-text data. That's better for your scripting/automation needs.
[Rant:
Afaik, POSIX standardized what people did and agreed on at one point in time, warts and all.
For example, whitespace is a nightmare... in sh, var=$value vs var="$value", look at warts like "$@" and the ever-present annoyance of handling of paths with whitespace. I'm not even going to go look to see what of these are mandated by POSIX. Multi-OS scripts are different, doing something like Oil (oilshell.org) or PowerShell makes a lot of sense...
]
Again, it's just because sometimes things are different. That's why I used pies and trucks as an analogy. Both pies and trucks are well established, serve their needs well, have plenty of variety, and room for improvement and innovation. That does not mean all work on desserts and automobiles should contain crusts and beds. Those are design decisions that serve some purposes very well, but not everything.
Most importantly: programming, like baking and automobile design, is an artistic craft, not just a solution to real world problems. We as a society already have well established solutions to tasty treats, transportation, and interacting with a computer. Trying something new will not harm anything, but there is a chance it may revolutionize everything. If it meets the authors requirements, while satisfying their creative urge, then the cost is well worth the benefit. Even if they are the only ones to ever use it.
That said, if you are asking why is it worth it for you or anyone else to invest their time into learning how to use it, that is a very different question, and I have no idea. I will not be using this any time soon, but I wish them luck, and I am glad that they are trying something new.