They are not investments which increase in value to offset the credit card debt incurred. Examples of useful kinds of debt include loans for education, investment and purchases of real estate. Credit cards are not the ideal way to get this sort of credit. Many people are tempted by the possibility of transferring their debt balances to a different credit card account with a lower interest rate. This sounds good in theory but can be very difficult to achieve in practice.
Credit institutions run credit checks on consumers before offerring accounts.
A large unpaid balance on another credit card is bound to show up on such a check. Credit card companies are unlikely to desire such a customer for an account. Certainly not at an interest rate overly favorable to that consumer, considering that such a consumer is a high credit risk. If you have undisciplined spending habits, you should actually consider reducing your credit limit rather than increasing it. Although most banking institutions charge a transaction fee on them, debit cards can be a way of restoring some discipline to your spending habits.