I don't know if you're willing to consider it evidence, but I think Apple's success is in large part due to their software and their UI's. iOs in particular.
Also, user interfaces might be closer to fashion than you would think! If you consider Windows XP's look. Imagine Windows 10 looking like that. Or consider Windows 8's different looks compared to Windows 7's. Or Google "material design" on Android Lollipop. Dang, this is exactly like fashion! :D
Is the UI of a piece of software actually a fashion statement?
Should these decisions not be evidence based in some way?
(I use Firefox 39 on Linux and have no strong opinions either way - just interested in the process)