Some offices give employees time off during holidays, but others don't. Some even make employees come to work on Christmas Day or during other festive seasons.
For me, I don't think it's fair to make an employee work during holidays. I think it should be voluntary - if you want to come to work, you can, but if you don't, you can stay home and celebrate with your family and friends.
Giving employees official holidays during their festive seasons should be part of their benefit package. I say "their festive seasons" because Christians may want to celebrate Christmas, Muslims may want to celebrate Eid al-Fitr, and Hindus may want to celebrate Diwali.
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.
By doing this, you prioritize employees' satisfaction and well-being. This is why people don't leave jobs, they leave toxic work environments. When you make people feel comfortable and loved, they will stay, and it will increase productivity and mutual respect.
Closing offices during holidays for like two weeks might affect business revenue, but how much?
You've been working from January to December, you should have sustainable investments and is it worth making employees miss out on time with their families and friends? I don't think so.
But what do you think about making someone's work mandatory during holidays?
This is completely unrealistic, at least in the way that you've posed it, and totally incompatible with the way the business actually works. You speak about Christmas as if it is a holiday isolated to religious Christmas - when it has completely morphed and detached from any religion at this point. More non religious people celebrate this in countries like the UK than religious followers. Also, the idea that a workplace somehow has an equal split of all religions is also completely off base and unrealistic - in my experience if a company has a large amount of religious followers of any kind, they will often be of one particular group and this rules out your "splitting the days" type setup. Companies are also very flexible around holidays and expect people to book time off but do not shut down completely.