A hechsher like the Rabbanut has a tight balance to make. Their mission is to promote torah observance by making kosher food available to those who may otherwise eat non-kosher food. They also promote shabbos observance by having certain requirements. Sometimes those goals are contradictory. This leads to the distinction between restaurants and hotels. If they would fully restrict being open on Shabbos in a hotel that is very likely to push the hotels to not have any level of kashrus at all and everyone who comes to the hotel will end up eating non-kosher food unless they make the effort to go elsewhere. In a restaurant, they will either go to the kosher one or the non-kosher one. An airport is somewhat similar to a hotel. If they fully restrict shabbos then the establishment will end up with no kashrus at all and the establishment will be open with anyhow with Jews doing everything while if they allow the same leniencies as a hotel the establishments will at least have non-Jews doing most of the work and there will be the kosher food eaten.
Indeed. It's a tough situation to be in, and if I am not mistaken I read somewhere that they consulted with R' Ovadia Yosef and got instructions to act as they did in the airport. Unfortunately there are very few poskim with ברייטע פלייצעס on the one hand, and יראת שמים on the other hand, that are willing rule on such delicate issues.
The only reason for my earlier post is to point out that there is a fundamental difference between a hotel and an airport restaurant in that the airport restaurant can't ever have Jewish customers on Shabbos that aren't unfortunately מחלל שבת, whereas in a hotel it is entirely possible to have people dining without any חילול שבת.