This is like sending an unsolicited email to someone who might want to buy your product.

A single instance is not a bad thing, but once it becomes a repeated occuance it is terrible.

With this particular case, the threshold is likely to be in expectation. If you approach people and any of them are aware of this concept in advance, they might feel used. If they know what you are going to do before you start talking then the entire atmosphere has already been polluted.

It might be easier to think of it in ecological terms. Sustainability and limiting harms mark the core of what should govern human endeavours. If the bar was considered an ecological environment, the harm would be in negatively impacting the enjoyment of customers. A single query from a stranger might do no harm. It might even enrich their evening experience. Done unsustainably however, results in a progressive reduction in the quality of experience across the ecosystem.