I can see how someone would make this mistake. On the other hand, it’s not hard to see why this is a bad idea.

Here’s the situation. Approaching or propositioning anyone while they’re at work is going to come off poorly since they’re backed into a corner. They’re a captive audience, as they must be in that space in order to get paid. In the case of retail, not only are they supposed to be nice to you, but they often can’t physically avoid you lest they get in trouble for poor service. In the end, the already hard job of saying “no” is made much worse by compounding it with proper workplace behavior. And even if they would find your advances interesting in any other setting, it’s the workplace that’s likely to sour things.