It's not you
The other day I was at the meat counter in the grocery store, and I was curious about something I hadn't seen before, so I asked the butcher, "How do you cook that?" She replied "How do I cook it?"
I was a bit taken aback, since I was just asking in general, not about her culinary proclivities. In other words, I intended you in the impersonal or generic sense, like one in more formal speech. I wasn't trying to be personal, but that is how she interpreted that you.
In this case, the misunderstanding wasn't serious. I clarified that I wasn't asking for her family's secret recipe [no, I didn't really say that], just for general information, and she explained.
However, I probably shouldn't have been that surprised, since I have heard other instances of you being misinterpreted, with more serious consequences. In these cases, it has been a customer service (or lack thereof) interaction, where the customer says something like "You promised it would be delivered in two days." In these cases, it has been obvious to me, the observer, that the service representative did not make the promise, but either another representative had or the company's policy made the commitment. In this case, the customer was using you in a general collective sense: "You, the people of company X." Unfortunately, the service representative, like the butcher, typically interprets you as referring specifically to them, expresses denial and/or indignation, and things go downhill from there.
I still find it mystifying, though, why the non-specific use of you seems to be disappearing.
So all "you" people out there, it's nothing personal...