I worked at a large bank for seven years. Tellers are the worst-paid employees but have the most direct customer interaction. One of the jokes made in banking is that you can tell who are the most important/well-paid people - the more $$$$$$ they make, the less they deal with the public.
In fact, at our bank, virtually no one from Asst. VP on up EVER directly dealt with the public. Only business, investment, or large facility loan customers.
I would imagine most tellers are like the ones at our bank, where large transactions engender a question about utilizing the bank's investment options.
They were expected, instructed, and RATED on doing so. They were dinged on performance appraisals if they did not do ask.
I just smiled, and politely say I have no need of their services right now.
I see no reason to be obnoxious or rude to lower-level employees. I have been in their shoes, and there is a good reason why I GOT OUT of public customer service jobs. I did not enjoy people dumping on me just because they could enjoy being mean. But it definitely makes you appreciate the people who are smiling and pleasant, even as they say "No thanks!"