Early in my career I was a sysadmin for a multiuser system, and I often had to go to people’s desks to troubleshoot problems they were having. That meant using whatever pointing device and keyboard they had. There were a crazy number of variations, including left handed setups of different types. It was actually an interesting part of the job. But yes, some left handed folks do that, as did some people who had issues with their right hand/arm.