Shlomozalman, that’s very nice, but not usual or excpected.
Pahutah has the right idea, it is a matter of mesnchlechkeit, not a chasunah issue. Also, when you compliment a wait staff member to the boss (and I do it in restaurants all the time, as it is quite easy to find the manager, not as easy to do it at a simcha), it lets them know they have hired a valuable employee, and perhaps it will make the manager look at that employee with a bit more appreciation. So often people complain when things are NOT done as they wish, but how often do we acknowledge when someone gets it right?
I also call the flower guy after my daughter’s wedding (we used a flower gemach rental in Boro Park), the owner/manager was such a pleasure to deal with and they did a magnificent job at an extremely fair price. When I called him the next day to thank him for the beautiful work they did to enhance our simcha, he was astonished, and his response was, “WHAT a nice lady you are! I can count on the fingers of one hand how many people have ever called me back in all the years that I am doing this.” I expressed my surprise that this was the case, because my husband and I are very big on hakoras hatov, but apparently some folks feel if they paid for it, they deserve the thanks for giving the guy parnassah. I don’t feelt hat way.