Bash does not forward signals like SIGTERM to processes it is currently waiting on. If you want to end your script by segueing into your server (allowing it to handle signals and anything else, as if you had started the server directly), you should use exec, which will replace the shell with the process being opened:
#!/bin/bash
echo "Doing some initial work....";
exec /bin/start/main/server --nodaemon
If you need to keep the shell around for some reason (ie. you need to do some cleanup after the server terminates), you should use a combination of trap, wait, and kill. See SensorSmith's answer.
