There must be some different kind of worldview here.. I guess it must have something to do with coming from a tipping culture vs a non-tipping culture. If I imagine myself, in my current job, dropping by a customer and deliver the updated product, and then the customer tries to hand over a fiver. I would go, in my mind, "What? What am I supposed to do with that? Do I look like a beggar that just happened to bring the product? I have a wage, I don't need to be "supported" with breadcrumbs by someone who think he's above me. I'm not a dog." And so on. It would definitely put a sour taste on everything. And actually my company's code of ethics (we're a worldwide company) do forbid receiving anything from customers, with the exception of the occasional shared lunch.