This is also a way to promote diversity in the workplace. If Christians take Christmas off, Muslims and Hindus can work, and then when Muslims take Eid off, Christians and Hindus can work. This way, you can regulate your workforce and give employees the freedom to celebrate their holidays.
I would say it doesn't apply to all countries. Because in our country Muslims are about 95% and people of other religions are about 5%, as far as I know there are no Christians in our country. Now in any company or government institution in our country Muslims must be more and Hindus and other religions are very less. Now if Muslims are given Eid-ul-Fitr holiday in our country, then it will be possible to run the institutions with Hindus and other religions? Of course not it will not be possible to run the institution. But if Christmas and Hindu festivals are given holidays to Hindus and other religions then it will be possible to run the institutions with Muslim people. So in our country there are holidays for major festivals of all religions.