I think this is a primary reason (100% plagiarized)
It’s a bit of a reverse mind-trick, but credit card companies like to see a low credit utilization rate. This is the percentage of credit you are using of the total amount you have available from all sources. If you carry $10,000 on a card and have $40,000 in total credit available, your utilization rate is 25%. If total credit is raised to $50,000, your utilization rate is 20%.
The idea is that by giving you more credit, it “relieves the pressure” on the utilization rate. You may become a better risk if you have more credit available, but then do not use it or use just a bit of it.