I agree with this entirely. But, the choice of a customer to show appreciation for the specific work which is done by specific employees is always appreciated by those employees and will be remembered. This is especially true when service calls come up or if there are any issues with the system at all.
Required? Not at all!
Appreciated? Yes, it is. It may allow a husband (or boyfriend) to take his girl out for a nice dinner, which just makes everyone a bit happier.
Not only have I never heard this, the logic doesn't make sense. A person works hard and does a good job in their day job, for doing this, they get a tip, so they will then go work a side job? Generally speaking, if people are working side jobs, they are working side jobs and it is often against company policy.
Then they don't get a tip, and could end up fired, and it certainly has no bearing on them receiving or not receiving a gratuity for a job well done.
As I said - this is something I agree with completely.
I just have not seen, in the last ten years, any employee who wasn't extremely grateful for a gratuity given by a customer. Or an employee who complained because a customer did not tip. Generally, it is NOT expected, nor demanded, and it is always very much appreciated.
Just as food from customers is not demanded, but appreciated. Heck, I remember one customer who made us fresh cookies everyday on the job site. Everyone working there very much appreciated it. No tip, but I still remember the cookies.