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.

i mean you're also throwing away security fixed running an OS that out of date, but the person doing this probably doesn't care about security anyway.