I did talk with manager about this and he explained the hours and work they did.So you're admitting you're self-centered? The "10 seconds" the kid had to take to get your salad could be just as important to him as the 10 minutes of your time it takes someone at your shop to browse bikes is to you. It's all relative, and only the person taking their personal time to help someone (mind you time that they aren't obligated to take) knows what that time is worth.
For all you know, the kid could have been covering for someone else and already been there hours longer than he was supposed to be, and could be late/almost late to something. Point is you don't know, nor have the decency or common sense to think like that and be passive.
And don't forget, I stay late all the time, so I actually do know.