The short answer is that you should only purchase these products when you can't qualify for traditional policies. Basically, if you have health issues that preclude you from buying life or disability insurance, credit life and disability insurance products can help you mitigate the risks of death or disability rather than going without any coverage at all.
Generally speaking, the policies that are sold in conjunction with a debt that you owe such as a credit card, auto loan, or mortgage are designed to pay a specified benefit such as a minimum payment during a disability or a flat dollar amount if you die. These policies require considerably less medical underwriting than their traditional counterparts and will cost more per dollar of coverage as well. Even with the added expense it's still a better deal than having no coverage at all.
For this reason, it's important to assess your gaps in insurance coverage and make any adjustments that may be necessary. If you are paying for credit insurance products and are healthy, you should shop for a traditional policy and compare cost/benefit ratios. You'll likely find that you're paying too much for your insurance.
On the other hand, if you have health issues that make it impossible to find affordable coverage elsewhere, consider buying credit insurance--particularly on your mortgage.
