In a way we’ve come full circle. Synths were really in during the disco era. They’re primitive, but this 1979 Alien trailer isn’t that far off from what’s going on in the Prometheus trailer.
The trend in the past year or so has been towards more synth-driven trailers. The Carmina Burana trend has long played out (though you still hear that a lot for network TV shows). Now it’s about unusual ear candy.