Because there are different religions so people do't just celebrate Christmas they also celebrate Hanukkah and Kwanzaa and other holidays so happy holidays is a better thing to say.

Because not everyone celebrates Christmas people from different religions celebrate different things such as Hanukkah and Kwanzaa, so happy holidays is a better thing to say.

People are doing test to make sure people don't have ebola and not just for the U.S. They are doing it so that people around the world stay safe and it wouldn't be fair to keep people confined to places with ebola because then perfectly healthy people wouldn't be able to leave the country.

some people do not celebrate christmas

There are other different tpes of holidays like Kwanzaa, Hanukkah, Christmas and New Year!

Some people celebrate Hanukkah (I hope I spell this right!) and Kawanzaa and it's also New Year's.