This would give bosses more of a reason to push certain employees to continue to work or continue education of children that do not believe in them. If you haven't subscribed to the belief of being a Christian, Easter and Christmas should not give off days for you. Those holidays having off days exist so those that do believe in Christianity have the day off to celebrate them. Islamic, Judaic beliefs also have their own holidays off days. Christmas and Easter should not be forced off holidays for those that do not believe them because that is forcing beliefs on them.
If a Christian gets a certain number of holidays off, then an atheist or someone of another religion would have to be allowed the same number of holidays. The others could either take their own religious days off or extend the other holiday. Problem is, many businesses shut down over holidays. With only 1/4 the workers, how are they going to conduct business. Odds are, many of these places will just keep the old system. The only other option is for them to take away religious holidays for everyone.
The same problem would exist for schools.
Easter and Christmas are basically pagan holidays: but I notice that Christians are celebrating them.
Today, the religious affiliation of these holidays is very minimal and only included by the religious.
Adults who don't believe in Father Christmas or the easter bunny still partake in festivities and people, even though they don't believe in ghouls or monsters, celebrate Halloween; without even celebrating the religious holiday after it, St Hallows day!
Public Holidays are for everyone, for the simple fact is you can't cater for all the different people and their specific situations, it takes too much work to organize for a single day.
For example what if at your work place, the boss/workplace supervisor/other important specialists had the day off, while a handful of the staff turned up to work not being qualified to do everything at the workplace to get a real days work done. It varies from Job to job but many workplaces could not function.
That and it would be political suicide for a politician, to take away many voters public holidays.