One sentence on MDN without any cited references doesn’t really afford any sort of “victory” over Adam’s contention.
I’ll also provide a statement without any cited reference. I’ve been working with web technologies since they first arrived on the scene when I was going through my CS program in university in the mid-90’s.
I recall discussions way back when around form elements indicating that browsers would respect the design and behavior of the existing widgets of the OS — there was no valid reason why Netscape’s (as an example) buttons, text fields, radio buttons, menus, etc. should look drastically different from the OS the user had on their workstation/computer — so it made sense to rely on the OS for this rather than invest resources trying to reinvent the wheel, so to speak.
Keep in mind what the original purpose of the World Wide Web was. Tim Berners-Lee didn’t go into this thinking about marketing splash pages, corporate branding, animations, etc. —there wasn’t any consideration for custom styling buttons, having images slide around the screen (there weren’t even images in the first few iterations!).
Of course, this is all just from my recollections of discussions and articles I read 20 years ago, but I’ve cited exactly as many references as CarissaLynn73, stuart, kscarfone, and the rest of the contributors to the MDN page did. ;)