I'm no expert here and definitive not a bank exec but it just doesn't make a business sense to take you in. With 12 cards and a utilization of less than 5%, you clearly don't spend enough to need another card.

btw I had a utilization of 30% - 40% (mostly business expenses) and was approved for a number of cards including Amex Plat even through I did not have any credit history. I assume it was likely the combination of high utilization and low credits that showed that I'll likely be going to use the card.