Things fail in the weirdest ways in unsupported environments though, it’s not like the “make transfer” button doesn’t work, it’s more like it might not even show up in the first place. Having 99% of your website work and the last 1% not work is a dealbreaker in many cases, and these “the site may not work for you based on your OS” banners lead the user into thinking it does work 100% if it works in 99% of the cases.

Not saying this is the way it should be, just saying that “doing your best” to allow unsupported platforms often leads to a terrible and confusing user experience.