Some owners who would rather pre-empt any problems by having their new watch serviced. These reps aren't assembled in clean room conditions and it's possible the person who put your movement together might be skimping on the lubrication in order to take some oil home to use for cooking. However, this is very much a "maybe" scenario, and your watch could run without any issues for years. So I'm with Nikz19 on this one - I don't have mine serviced unless/until a problem occurs.