respawn-pane command can resurrect a "dead" pane that hangs around if the original process it's running exits when the
remain-on-exit option is
on. What is the intended use case for this feature? I'm guessing there is probably some cool use for it but I'm unable to think of what that might be.
It is for convenience. It preserves the starting command and position of a window or pane - it is often easier to do respawn-pane or respawn-window than to recreate a window or pane. This is particularly the case if you have windows which always run the same application in the same place.
It also keeps the pane history and the exit status in the process of a pane (or all panes) so you can look at them even if the pane has exited.