While that could set off an alarm sometimes, there are other reasons. I recently bought my Samsung Laptop from the Microsoft Store from the Galleria mall near me. The sales person I was working with told me it was a chance that Debit/Credit card would be declined (BofA), as for some reason, a large order is flagged as potential fraud. She was right...and the card was swiped, not entered manually. I just gave her my actual credit card, (not my debit/credi) from Capital One, and it went through right away. I just went home then and sent a payment to my CC.
So, while it's frustrating, I could see this happening due to Credit Cards.