I was an SFSO in 1991/2, and it was certainly taken seriously by everyone then. I witnessed a crash at Valley in 1986 where the wreckage also ended up tumbling across the airfield and ending up in front of the tower. Two aircraft had just taxied, and a friend next to them amazed himself with his unstrap and egress speed in response to a wildly gesticulating liney. The crash alarm only went off for about half a second because the local controller, having dispatched his finger towards the crash button, then realised the path of the flaming cartwheel was straight at him and started running. His finger thus only grazed the button.