This is one of those things you really, really deeply have to question. How much money (via dev time) do you spend on supporting such very old legacy content vs the derived value of said customers? Some people DO have that use case, and for them it is their lot to suffer. But that's clearly not he story presented in the link.

Same deal with mobile OS support, really. You have to have a pretty unusual or long-standing audience to support anything pre-4.2, let alone pre-4.0. iOS7 is also probably not worth the time to target for most products.

or ie10...

IE10 supports flexbox, it just supports the 2012 syntax.