A Kill Switch seems most relevant when someone wants the VPN connection to have predictable behavior during interruptions. It is one of those features that may not be noticed while everything works normally, but its purpose becomes clearer once you think about a dropped VPN connection. On Android, it also makes sense to look at the other available controls at the same time, because different people use their phones in different ways. Some may care more about selected apps, while others may focus on connection types, privacy settings or simple everyday operation.