What is the benefit? It takes time to start/stop a Tomcat server. Not much, compared to its bigger relatives, but still it takes time. Keeping both nodes in a cluster alive means millisecond-speed failover instead of tens of seconds or more. And it's not like Tomcat is a major resource hog.
Customer surveys are for companies who didn't pay proper attention to begin with.
subject: can tomcat cluster only leaves one server up, if that server is down, then start the second server?