Maybe you are really bad at teaching your students then. The "basics" of word processing, using a spreadsheet, or creating a presentation typically apply across most office suites. Rather than teaching students to memorize exactly how Microsoft wants you to do things why not teach them to think logically and learn how to "learn" and adapt.

When I was growing up and going through grade school MS Office didn't have the monopoly it does now. I learned on Word Perfect, a bit on Lotus products, and some other package on an old Apple. Today, unfortunately, I have the great pleasure of having to work with MS Office all the time. I am still able to do my job, and quit well. So did not learning MS Office specifically in high school disadvantage me? Absolutely not!

Teach your students...don't brainwash them