While I do not know whether it was related to them trying to learn about your current income, I have had very few instances where the retailer has informed me that my card was blocked and that I needed to call in. These were related to irregular/out of pattern spending, such as multiple large charges in a single day, or the one time when I drove from Calgary to Victoria and made multiple gas stops along the way - at the third stop, I believe it was in Hope BC, they blocked it, and once I called, they advised that it was triggered by the use of the card miles apart in one day.

I also know of a couple of people whose cards were blocked because the cards were also used half way around the world in the same day. When they called in, they realized that the numbers were actually stolen.