Wondering what your income was if you don't mind me asking?
FYI, the T&C on the website says the minimum line, if approved, is $5000. So it's not the experience that determines whether you get the $5k line, it's whether they'll approve you or not.
Yes this is true because its a Visa Signature card, but Chase at most times will not approve you if you do not have any experience with $5K line of credit if it does go in to a manual review. Its just another excuse not to approve someone IMO.