Airline question: Why would they need to know?

So Air Tran called me today. There have been some changes to my flight times and the called to let me know about the changes and to see if the changes were okay. I told the lady on the phone the flight times still were okay, I just needed to contact the cruise line to change my shuttle pick up times.  The very nice lady on the phone (yes she was very good at her job, she was nice, but stayed on point and stuck to the facts…really it was great customer service) , mentioned that it didn’t say on my reservation that I was going on a cruise, so she would mark that on my account to help expedite my luggage. Okay that sounds great, but I’m not sure what that means. Yes I know what “expedite luggage” means, but I’m not sure what I means in this context or if that was something I was supposed to know to tell the airline?