All businesses and people I interact with or travel to use PC. I would be very limited in accessing my data do or collaborating with others if I used Mac, also the cost would be very high. I use Excel with macros, Word, PowerPoint (where I typically have to add my data to a shared presentation) and a few specialized tools. I can use my home computer to do many work related tasks if a quick need arises, using MS Office that only cost me $10 via some kind of employer sponsored program. I can't use free suites like OpenOffice because they don't maintain the formatting of presentations and spreadsheets very well. If I had a Mac, I'd need to do everything on my work laptop, which is a chore sometimes.
Of course if I was in a profession that doesn't require much remote collaboration, or odd graphics / publishing, Mac would be rest.