Mandatory where? it is already the preferred format of the British government, and I think I have read about other adoption, and as well as some governments adopting open source office suites which would push them towards ODF.

Other governments could follow, but the private sector is reluctant. Even Airbus which is a high profile move away from MS has gone to Google Docs.

Because https://en.wikipedia.org/wiki/Embrace,_extend,_and_extinguis...