"Not necessary" doesn't mean it's not still fair use. Lots of things aren't necessary but one definition or another. The argument here is that it's lack of necessity makes it incidental.

Here's the Carl Benjamin case covered in bloomberg (you can look up the specific case if you'd like) https://news.bloomberglaw.com/ip-law/youtuber-wins-attorneys...

> Copyright violations don't require the copyright holder to prove commercial harm. That's the entire point of statutory damages.

This is explicitly one of the four points of fair use as stated by the US government, so it's very important.

https://www.copyright.gov/fair-use/more-info.html