In the fundamentalist church setting in which I was a member, we were taught that the use of "Xmas" meant that Christ was being X'd out of the holiday season. Maybe you have heard that too. Guess what? Xmas is not anti-Christian as I had been taught by the church. It's actually the opposite!
Instead of taking Christ out of Christmas, the "X" in "Xmas" is the symbol for Christ. Mignon Fogarty explains:
In Greek, the letter "chi" is written as an X, and chi is the first letter of the Greek word for "Christ." Greeks sometimes abbreviated "Christ" as "X." For example, they abbreviated "Christ savior" as "XP." ("P" is the symbol for the Greek letter "rho," which is the first letter of the word "savior" in Greek.) The Oxford English Dictionary shows the first known English use of "Xmas" in 1551.
It's easier and shorter to write "Xmas" and it may have a religious origin, but most people are unaware of its religious origin.
The only reason we still have Xmas and Easter is because early Christians tried to take over Pagan holy days by "Christianizing" them. If they had left things alone, it's likely these two holidays would have been as forgotten as other Pagan days of service. Wouldn't that have been sad for retailers?