Normal
Maybe the crew or line doesn't think it is fair for the servers of the passenger who won big in the casino get a huge tip that could or should be shared among them all. There is also the plain old big tipper and plain old cheapskate issue. I think the fact that pooling tips tends to even out their periodic income, instead of maybe having a very small pay period occasionally, is more desirable than a big windfall once in a while. It could be this method will cause slackers to be "encouraged" to improve, by those that they pool tips with.