Comment: Tradition?

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In reply to comment: Well then why does this one (see in situ)

Tradition?

Google "history of tipping". It's to ensure prompt service. A cashier or DMV employee is not bringing you anything, let alone something you are putting in your body. A cashier or DMV employee is not keeping one eye on you, making sure your drink is full or your food is cooked properly or you need a new napkin or you are ready to pay...

And if the band you're in starts playing different tunes, I'll see you on the dark side of the moon.