No credit IS bad credit.
You don't have to carry debt to have a credit history, but you do have to use credit to have a credit history. If you haven't used the system, they have no knowledge of your crdit worthiness.
I use credit cards as a tool to protect my finances and purchases (fraud protection is greater with CCs than a bank account/card, as well as being able to dispute transactions where service was failed to be delivered or inadequate). I also always pay off my statement balance in full every month.
I do my best to only buy things I can afford to pay in full, but a home and automobile can be exceptions to that (even though I bought my auto in full due to a financial windfall). But I still participate in the system to gain the benefits of the system
www.nerdwallet.com is a great resource on credit education and provides a wealth of tools for starting build your bad credit to good credit.