A variety of reasons exist for wanting to know how to increase your credit limit.
The most obvious is that your credit card balance is running up against your existing credit limit, and without a credit limit increase you will max out your credit card and not be able to use it until you pay down the balance.
But you might also want to increase your credit limit (even just temporarily) to afford a very expensive item. Many people do this just so they can collect a large batch of
Or, maybe you want to improve your credit score. An increased credit limit will immediately reduce your credit utilization (how much of your total available credit you have already used), and credit utilization is one of the factors that determines credit score, since lower credit utilization typically improves a credit score.