What are the aspects of working on a bus that make it impractical? When I find myself in your position usually I end up realizing I'm self-conscious about people seeing what I'm doing more than I'm concerned about any practical downside or benefit.

In my case it's mostly the shaking - trains are mostly fine, but buses are just too unstable. They also tend to be more crowded, meaning I need to tuck my elbows in and adopt an even-less-stable position which compounds the problem.