It's really quite simple. A credit history gives the lender information as to how you handle your financial obligations. Lenders need to know that you have good credit habits. That's definitely not something you develop overnight. You need to have at least one year of credit history to be seriously considered by most creditors.
Some creditors have even stiffer requirements.
Every time you apply for a credit card, department store card, or any other type of credit-related card, an inquiry is made as to your credit status. This inquiry is noted with the respective credit bureau. Although these inquiries will remain on the report for approximately one year, issuers will be primarily concerned with the number of inquiries over the last 6 months. Showing a handful of inquiries for that period is not critical. But issuers do become concerned if there are more than 10 inquiries during that time.