I assume people change it from ^B so it still works in vim and less - that's why...

kurtisc on Sept 16, 2018 | parent | context | favorite | on: Getting started with Tmux

I assume people change it from ^B so it still works in vim and less - that's why I changed it - so I find the popular ^A prefix particularly baffling, given how useful it is with programs that use readline i.e. every shell.