Comment by Delk

People probably feel less in control in an unfamiliar environment even if the superficial functionality is similar. I suspect this might be a greater factor for those who are somewhat tech-savvy and used to knowing their way around their computer to some degree. Once you go a bit beyond launching apps and using their UIs, the differences become apparent, bringing about a sense of unfamiliarity and a loss of a sense of control and competence.

People for whom the computer is just an appliance with limited applications (and who recognise their relationship to the computer as such) might even be better able to switch, provided that everything is set up for them. My elderly parents used a Linux box I set up for them for years at some point.