I think parts are trendy because everyone goes out and buys them because all the pros ride em. Honestly most people don't even need those parts. Just get a RUP, throw some better bars on, get some Vertx wheels or demon cores and a new headset and you're set for a while until you start snapping fork tubes or bending the shit out of your forks while landing, not bailing.
Trendy parts are the stronger parts that people use, but there are also good alternatives that you might like so just look around and start your own trends. The only way the sport will progress is if you get other brands products and review them for the companys and riders to know.