Corollary: the extent of fashion-driven variability those "tools" support over generations tells us just how little utility those tools provide.

In actual tools, the form and function are strongly connected. Tools of competing brands look pretty much the same, except for color accents, because they can't look any different without sacrificing functionality, performance and safety characteristics.

You don't see power tool vendors trying to differentiate their impact drivers by replacing rubber handles with flat glass because it's more "modern", because it would compromise safety and make the tool unsuitable for most jobs its competitors fulfill. This happens in software mostly because the tools aren't doing much of anything substantial - they're not powerful enough for design to actually matter.

I do see tool vendors often adding their own logos to the tools. They choose non-functional colors for styling. They'll make something more rounded or more squared for aesthetic reasons. For consumer-facing tools there are lots of little non-functional changes they'll choose to do for their own stylistic and branding purposes. They do want to ultimately differentiate their products from competitors, not just be the exact same as all the others on the shelf.