It was purportedly (and probably in actuality) intended as a survival aid to be used after landings and before recovery in the Siberian wilderness, although allegedly was intended as a defensive weapon against in-space attacks by the US space program.
Possibly also for suicide if you get into a situation where you would slowly suffer to death?
I’d rather take hypoxia atleast then it not technically suicide.
A gunshot wound to the head is also not suicide.
If however both the gunshot wound and hypoxia are self inflicted then it is suicide, regardless if you pull the trigger or open a valve.