I think there's something to be said for the authenticity of real orchestras. No matter how good your synthesizer is, it can't stand up to a real acoustic sound (unless, of course, you're using a real synth lead or pad, rarely used in musicals anyway). I know sometimes synthesizers are an advantage - my high school just used a few in our production of Once On This Island because we didn't have enough people to learn things like all the steel drum parts - but I would've rather had more of the real thing if we could have.

Cloakboy, how come you hate musicals and theater? Acting (and teching and pit, too) are so much fun!