I have to agree with the individual who suggested that a passenger that spends a lot of money onboard seems to be eligible for fast track. When we cruise, my wife and I tend to buy nice things in the jewelry stores, go to the specialty restaurants, make several trips to the spa. I've spent only $40 in the casino. I believe that's why we were bumped to Platinum.
Also, it's very easy these days for companies to understand how consumers are interacting with the competition. So Princess must have known that we had a few sailings on Royal Caribbean too.