Adding to this: without any specification, the browser should, and does, use the operating system's native controls when rendering controls such as <button>.
https://blog.chromium.org/2020/03/updates-to-form-controls-a...
All part of Google's master plan to commoditize desktop OSs. Everyone outside the US already uses Android, soon your computer will be a Chrome box instead of a Windows/Mac/Linux box.
First they did the browser title bar & tab bar integration/styling & removed the normal OS title bar, then they made Chrome OS, now they are removing the last traces of OS-specific styling for those who haven't already switched to Chrome OS.
And Gmail, Gdocs, and Chromebooks are huge in kids schools. The kids don't know anything outside the non-Google universe. Most of the kids I know think MS Word/Excel/PowerPoint are lame (not that I'm a fan, but you have to admit MS Office is unrivaled in its abilities).
20 years from now they will have a gigantic monopoly over a huge range of computing.
Wait until they reach the age and get hired in a corporation. I am a die hard linux user ( been on linux desktop more than i can remember ), but the latest stuff (=365) from MS is really appealing compared with gSuite. It has a level of sophistication that Google cannot reach.