Several reasons: RDP (found nothing that works as well as the integrated one of Windows), software (Altium, Adobe Illustrator). Regarding Illustrator, I might switch to Inkscape the day it fully supports CMYK color, spot colors, overprinting, and such things... for now I just feel it's not ready yet every time I try it.

And server-side: specific software I need to run for my team, like Autodesk Vault. For the rest, 95% of our servers run Linux.