We only have one CVS in town, and it happens to be very convenient on my daily trips back and forth to taking my kids to school. I've gone in at least 5 times per week, for three weeks. Most of the time I am looking at the same items.
The first week I did this, I was there bright and early and found only one Always Infinity (free after ECB) on the shelf. Later that day I stopped in again and found another single one on the shelf. Later in the week, I was in that ailse anyway, and noticed there was one on the shelf.
Maybe my store does this to limit the amount they give away or maybe they've had experiences with people with multiple cards clearing them out or maybe (and I'm reaching here) they want each and every customer to feel like they just won the lotto when really all they got was some piece of crap they might not have ever bought in the first place anyhow