Store cards definitely have their place in the credit market. Stores use them to get you to buy more as studies show that you are inclined to spend more with a CC vs. cash. They entice you into the store usually by discounts/promotions of some kind. For some, if you typically shop at a certain store, the discounts can add up. Or in the case with home improvement cards - they radomly offer 0% financing for longer than some CC's offer - also without the need to apply for a new CC to get the 0%.

I personally don't have any store cards yet, but if I develop a trend where I tend to shop at a store often and the rewards look good, I might app for one in the future.