> hilariously probably Windows

That's probably true.

> 15 y/0

It's a matter of expectations, many laptops that old still work decently enough with a refreshed battery. Funnily enough win10 was released 15 ago, and one can still get support for it for at least another 3 years until 2028, even on the customer license.

Will modern versions of those other browsers still work on an 8 year old OS, or has it been updated where it is no longer compatible? So much effort has been put into hardware rendering, and the mechanisms for the browser to interact with that hardware has changed within those OS versions. Forcing the user to download an older compatible version of the browser to work with the older OS is also tossing away potential security fixes.