Most CCC do not like PIF (Commonly Called Dead Beats) as they are not getting paid for you using their CL.
You are basically getting a 30 to 45 day loan for free from them for nothing in return. Why would they increase the amount they are loaning you for nothing in return.
Your Uncle is getting offers because he likely carries a small balance each month that they can then charge interest.
The reason he is getting CLI offers to is trick him into using more of the available CL and carry a higher balance so they can make more interest if he carries a higher but still low balance.
You have to pay to play in the CLI game.