There's nothing inherently "wrong" with a non-overclocked GPU. Some consumers don't feel comfortable with an overclocked card and want something that has been thoroughly tested at the stock speeds by both the chip manufacturer (Nvidia or AMD) and the card manufacturer. Besides, stock-clocked cards give you more overclocking headroom in terms of percentages. 800 MHz compared to 700 MHz (stock card OC) is a bigger improvement than 800 MHz vs 750 MHz (overclocked card OC).