Who is using a browser build that is more than 2 years old on the open web? Is that a sensible enough use case that it should be supported?
Any public service (aka government site) will have a huge amount of people on "outdated" software and hardware.
Also: how the f... did 2 years become "omg it's so old we're no longer supporting it"?
I hate it.
Any public service (at least in theory) must support browser versions significantly beyond the arbitrary 2-years-old mark.