The bars sold in the metal displays in the better hardware stores are about the softest I've seen. Easily bendable, but they do have some temper. I used to use 2024T4 for pack stays, only because it was stiffer than the hardware stuff and held its shape better to transfer weight, but still could be bent to desired shape.
Your mention of hobby stores is probably right - the aluminum stock they sell tends to be quite soft for making models. I've only seen much smaller dimensions, though (for models).